diff --git a/docs/en/docs/tutorial/query-params-str-validations.md b/docs/en/docs/tutorial/query-params-str-validations.md
index 549e6c75b..f87adddcb 100644
--- a/docs/en/docs/tutorial/query-params-str-validations.md
+++ b/docs/en/docs/tutorial/query-params-str-validations.md
@@ -277,7 +277,7 @@ You can also add a parameter `min_length`:
 
 ## Add regular expressions
 
-You can define a <abbr title="A regular expression, regex or regexp is a sequence of characters that define a search pattern for strings.">regular expression</abbr> that the parameter should match:
+You can define a <abbr title="A regular expression, regex or regexp is a sequence of characters that define a search pattern for strings.">regular expression</abbr> `pattern` that the parameter should match:
 
 === "Python 3.10+"
 
@@ -315,7 +315,7 @@ You can define a <abbr title="A regular expression, regex or regexp is a sequenc
     {!> ../../../docs_src/query_params_str_validations/tutorial004.py!}
     ```
 
-This specific regular expression checks that the received parameter value:
+This specific regular expression pattern checks that the received parameter value:
 
 * `^`: starts with the following characters, doesn't have characters before.
 * `fixedquery`: has the exact value `fixedquery`.
@@ -325,6 +325,20 @@ If you feel lost with all these **"regular expression"** ideas, don't worry. The
 
 But whenever you need them and go and learn them, know that you can already use them directly in **FastAPI**.
 
+### Pydantic v1 `regex` instead of `pattern`
+
+Before Pydantic version 2 and before FastAPI 0.100.0, the parameter was called `regex` instead of `pattern`, but it's now deprecated.
+
+You could still see some code using it:
+
+=== "Python 3.10+ Pydantic v1"
+
+    ```Python hl_lines="11"
+    {!> ../../../docs_src/query_params_str_validations/tutorial004_an_py310_regex.py!}
+    ```
+
+But know that this is deprecated and it should be updated to use the new parameter `pattern`. 🤓
+
 ## Default values
 
 You can, of course, use default values other than `None`.
diff --git a/docs_src/query_params_str_validations/tutorial004.py b/docs_src/query_params_str_validations/tutorial004.py
index 5a7129816..3639b6c38 100644
--- a/docs_src/query_params_str_validations/tutorial004.py
+++ b/docs_src/query_params_str_validations/tutorial004.py
@@ -8,7 +8,7 @@ app = FastAPI()
 @app.get("/items/")
 async def read_items(
     q: Union[str, None] = Query(
-        default=None, min_length=3, max_length=50, regex="^fixedquery$"
+        default=None, min_length=3, max_length=50, pattern="^fixedquery$"
     )
 ):
     results = {"items": [{"item_id": "Foo"}, {"item_id": "Bar"}]}
diff --git a/docs_src/query_params_str_validations/tutorial004_an.py b/docs_src/query_params_str_validations/tutorial004_an.py
index 5346b997b..24698c7b3 100644
--- a/docs_src/query_params_str_validations/tutorial004_an.py
+++ b/docs_src/query_params_str_validations/tutorial004_an.py
@@ -9,7 +9,7 @@ app = FastAPI()
 @app.get("/items/")
 async def read_items(
     q: Annotated[
-        Union[str, None], Query(min_length=3, max_length=50, regex="^fixedquery$")
+        Union[str, None], Query(min_length=3, max_length=50, pattern="^fixedquery$")
     ] = None
 ):
     results = {"items": [{"item_id": "Foo"}, {"item_id": "Bar"}]}
diff --git a/docs_src/query_params_str_validations/tutorial004_an_py310.py b/docs_src/query_params_str_validations/tutorial004_an_py310.py
index 8fd375b3d..b7b629ee8 100644
--- a/docs_src/query_params_str_validations/tutorial004_an_py310.py
+++ b/docs_src/query_params_str_validations/tutorial004_an_py310.py
@@ -8,7 +8,7 @@ app = FastAPI()
 @app.get("/items/")
 async def read_items(
     q: Annotated[
-        str | None, Query(min_length=3, max_length=50, regex="^fixedquery$")
+        str | None, Query(min_length=3, max_length=50, pattern="^fixedquery$")
     ] = None
 ):
     results = {"items": [{"item_id": "Foo"}, {"item_id": "Bar"}]}
diff --git a/docs_src/query_params_str_validations/tutorial004_an_py310_regex.py b/docs_src/query_params_str_validations/tutorial004_an_py310_regex.py
new file mode 100644
index 000000000..8fd375b3d
--- /dev/null
+++ b/docs_src/query_params_str_validations/tutorial004_an_py310_regex.py
@@ -0,0 +1,17 @@
+from typing import Annotated
+
+from fastapi import FastAPI, Query
+
+app = FastAPI()
+
+
+@app.get("/items/")
+async def read_items(
+    q: Annotated[
+        str | None, Query(min_length=3, max_length=50, regex="^fixedquery$")
+    ] = None
+):
+    results = {"items": [{"item_id": "Foo"}, {"item_id": "Bar"}]}
+    if q:
+        results.update({"q": q})
+    return results
diff --git a/docs_src/query_params_str_validations/tutorial004_an_py39.py b/docs_src/query_params_str_validations/tutorial004_an_py39.py
index 2fd82db75..8e9a6fc32 100644
--- a/docs_src/query_params_str_validations/tutorial004_an_py39.py
+++ b/docs_src/query_params_str_validations/tutorial004_an_py39.py
@@ -8,7 +8,7 @@ app = FastAPI()
 @app.get("/items/")
 async def read_items(
     q: Annotated[
-        Union[str, None], Query(min_length=3, max_length=50, regex="^fixedquery$")
+        Union[str, None], Query(min_length=3, max_length=50, pattern="^fixedquery$")
     ] = None
 ):
     results = {"items": [{"item_id": "Foo"}, {"item_id": "Bar"}]}
diff --git a/docs_src/query_params_str_validations/tutorial004_py310.py b/docs_src/query_params_str_validations/tutorial004_py310.py
index 180a2e511..f80798bcb 100644
--- a/docs_src/query_params_str_validations/tutorial004_py310.py
+++ b/docs_src/query_params_str_validations/tutorial004_py310.py
@@ -6,7 +6,7 @@ app = FastAPI()
 @app.get("/items/")
 async def read_items(
     q: str
-    | None = Query(default=None, min_length=3, max_length=50, regex="^fixedquery$")
+    | None = Query(default=None, min_length=3, max_length=50, pattern="^fixedquery$")
 ):
     results = {"items": [{"item_id": "Foo"}, {"item_id": "Bar"}]}
     if q:
diff --git a/docs_src/query_params_str_validations/tutorial010.py b/docs_src/query_params_str_validations/tutorial010.py
index 35443d194..3314f8b6d 100644
--- a/docs_src/query_params_str_validations/tutorial010.py
+++ b/docs_src/query_params_str_validations/tutorial010.py
@@ -14,7 +14,7 @@ async def read_items(
         description="Query string for the items to search in the database that have a good match",
         min_length=3,
         max_length=50,
-        regex="^fixedquery$",
+        pattern="^fixedquery$",
         deprecated=True,
     )
 ):
diff --git a/docs_src/query_params_str_validations/tutorial010_an.py b/docs_src/query_params_str_validations/tutorial010_an.py
index 8995f3f57..c5df00897 100644
--- a/docs_src/query_params_str_validations/tutorial010_an.py
+++ b/docs_src/query_params_str_validations/tutorial010_an.py
@@ -16,7 +16,7 @@ async def read_items(
             description="Query string for the items to search in the database that have a good match",
             min_length=3,
             max_length=50,
-            regex="^fixedquery$",
+            pattern="^fixedquery$",
             deprecated=True,
         ),
     ] = None
diff --git a/docs_src/query_params_str_validations/tutorial010_an_py310.py b/docs_src/query_params_str_validations/tutorial010_an_py310.py
index cfa81926c..a8e8c099b 100644
--- a/docs_src/query_params_str_validations/tutorial010_an_py310.py
+++ b/docs_src/query_params_str_validations/tutorial010_an_py310.py
@@ -15,7 +15,7 @@ async def read_items(
             description="Query string for the items to search in the database that have a good match",
             min_length=3,
             max_length=50,
-            regex="^fixedquery$",
+            pattern="^fixedquery$",
             deprecated=True,
         ),
     ] = None
diff --git a/docs_src/query_params_str_validations/tutorial010_an_py39.py b/docs_src/query_params_str_validations/tutorial010_an_py39.py
index 220eaabf4..955880dd6 100644
--- a/docs_src/query_params_str_validations/tutorial010_an_py39.py
+++ b/docs_src/query_params_str_validations/tutorial010_an_py39.py
@@ -15,7 +15,7 @@ async def read_items(
             description="Query string for the items to search in the database that have a good match",
             min_length=3,
             max_length=50,
-            regex="^fixedquery$",
+            pattern="^fixedquery$",
             deprecated=True,
         ),
     ] = None
diff --git a/docs_src/query_params_str_validations/tutorial010_py310.py b/docs_src/query_params_str_validations/tutorial010_py310.py
index f2839516e..9ea7b3c49 100644
--- a/docs_src/query_params_str_validations/tutorial010_py310.py
+++ b/docs_src/query_params_str_validations/tutorial010_py310.py
@@ -13,7 +13,7 @@ async def read_items(
         description="Query string for the items to search in the database that have a good match",
         min_length=3,
         max_length=50,
-        regex="^fixedquery$",
+        pattern="^fixedquery$",
         deprecated=True,
     )
 ):
diff --git a/fastapi/param_functions.py b/fastapi/param_functions.py
index 6ddce3468..5efd8b995 100644
--- a/fastapi/param_functions.py
+++ b/fastapi/param_functions.py
@@ -18,7 +18,12 @@ def Path(  # noqa: N802
     min_length: Optional[int] = None,
     max_length: Optional[int] = None,
     pattern: Optional[str] = None,
-    regex: Optional[str] = None,
+    regex: Annotated[
+        Optional[str],
+        deprecated(
+            "Deprecated in FastAPI 0.100.0 and Pydantic v2, use `pattern` instead."
+        ),
+    ] = None,
     examples: Optional[List[Any]] = None,
     example: Annotated[
         Optional[Any],
@@ -65,7 +70,12 @@ def Query(  # noqa: N802
     min_length: Optional[int] = None,
     max_length: Optional[int] = None,
     pattern: Optional[str] = None,
-    regex: Optional[str] = None,
+    regex: Annotated[
+        Optional[str],
+        deprecated(
+            "Deprecated in FastAPI 0.100.0 and Pydantic v2, use `pattern` instead."
+        ),
+    ] = None,
     examples: Optional[List[Any]] = None,
     example: Annotated[
         Optional[Any],
@@ -113,7 +123,12 @@ def Header(  # noqa: N802
     min_length: Optional[int] = None,
     max_length: Optional[int] = None,
     pattern: Optional[str] = None,
-    regex: Optional[str] = None,
+    regex: Annotated[
+        Optional[str],
+        deprecated(
+            "Deprecated in FastAPI 0.100.0 and Pydantic v2, use `pattern` instead."
+        ),
+    ] = None,
     examples: Optional[List[Any]] = None,
     example: Annotated[
         Optional[Any],
@@ -161,7 +176,12 @@ def Cookie(  # noqa: N802
     min_length: Optional[int] = None,
     max_length: Optional[int] = None,
     pattern: Optional[str] = None,
-    regex: Optional[str] = None,
+    regex: Annotated[
+        Optional[str],
+        deprecated(
+            "Deprecated in FastAPI 0.100.0 and Pydantic v2, use `pattern` instead."
+        ),
+    ] = None,
     examples: Optional[List[Any]] = None,
     example: Annotated[
         Optional[Any],
@@ -210,7 +230,12 @@ def Body(  # noqa: N802
     min_length: Optional[int] = None,
     max_length: Optional[int] = None,
     pattern: Optional[str] = None,
-    regex: Optional[str] = None,
+    regex: Annotated[
+        Optional[str],
+        deprecated(
+            "Deprecated in FastAPI 0.100.0 and Pydantic v2, use `pattern` instead."
+        ),
+    ] = None,
     examples: Optional[List[Any]] = None,
     example: Annotated[
         Optional[Any],
@@ -256,7 +281,12 @@ def Form(  # noqa: N802
     min_length: Optional[int] = None,
     max_length: Optional[int] = None,
     pattern: Optional[str] = None,
-    regex: Optional[str] = None,
+    regex: Annotated[
+        Optional[str],
+        deprecated(
+            "Deprecated in FastAPI 0.100.0 and Pydantic v2, use `pattern` instead."
+        ),
+    ] = None,
     examples: Optional[List[Any]] = None,
     example: Annotated[
         Optional[Any],
@@ -301,7 +331,12 @@ def File(  # noqa: N802
     min_length: Optional[int] = None,
     max_length: Optional[int] = None,
     pattern: Optional[str] = None,
-    regex: Optional[str] = None,
+    regex: Annotated[
+        Optional[str],
+        deprecated(
+            "Deprecated in FastAPI 0.100.0 and Pydantic v2, use `pattern` instead."
+        ),
+    ] = None,
     examples: Optional[List[Any]] = None,
     example: Annotated[
         Optional[Any],
diff --git a/fastapi/params.py b/fastapi/params.py
index c1bdaf1b4..53d30cc33 100644
--- a/fastapi/params.py
+++ b/fastapi/params.py
@@ -33,7 +33,12 @@ class Param(FieldInfo):
         min_length: Optional[int] = None,
         max_length: Optional[int] = None,
         pattern: Optional[str] = None,
-        regex: Optional[str] = None,
+        regex: Annotated[
+            Optional[str],
+            deprecated(
+                "Deprecated in FastAPI 0.100.0 and Pydantic v2, use `pattern` instead."
+            ),
+        ] = None,
         examples: Optional[List[Any]] = None,
         example: Annotated[
             Optional[Any],
@@ -51,7 +56,7 @@ class Param(FieldInfo):
             warnings.warn(
                 "`example` has been depreacated, please use `examples` instead",
                 category=DeprecationWarning,
-                stacklevel=1,
+                stacklevel=4,
             )
         self.example = example
         self.include_in_schema = include_in_schema
@@ -70,11 +75,17 @@ class Param(FieldInfo):
         )
         if examples is not None:
             kwargs["examples"] = examples
+        if regex is not None:
+            print(f"regex: {regex}")
+            warnings.warn(
+                "`regex` has been depreacated, please use `pattern` instead",
+                category=DeprecationWarning,
+                stacklevel=4,
+            )
         if PYDANTIC_V2:
             kwargs["annotation"] = annotation
             kwargs["pattern"] = pattern or regex
         else:
-            # TODO: pv2 figure out how to deprecate regex
             kwargs["regex"] = pattern or regex
 
         super().__init__(**kwargs)
@@ -101,7 +112,12 @@ class Path(Param):
         min_length: Optional[int] = None,
         max_length: Optional[int] = None,
         pattern: Optional[str] = None,
-        regex: Optional[str] = None,
+        regex: Annotated[
+            Optional[str],
+            deprecated(
+                "Deprecated in FastAPI 0.100.0 and Pydantic v2, use `pattern` instead."
+            ),
+        ] = None,
         examples: Optional[List[Any]] = None,
         example: Annotated[
             Optional[Any],
@@ -156,7 +172,12 @@ class Query(Param):
         min_length: Optional[int] = None,
         max_length: Optional[int] = None,
         pattern: Optional[str] = None,
-        regex: Optional[str] = None,
+        regex: Annotated[
+            Optional[str],
+            deprecated(
+                "Deprecated in FastAPI 0.100.0 and Pydantic v2, use `pattern` instead."
+            ),
+        ] = None,
         examples: Optional[List[Any]] = None,
         example: Annotated[
             Optional[Any],
@@ -210,7 +231,12 @@ class Header(Param):
         min_length: Optional[int] = None,
         max_length: Optional[int] = None,
         pattern: Optional[str] = None,
-        regex: Optional[str] = None,
+        regex: Annotated[
+            Optional[str],
+            deprecated(
+                "Deprecated in FastAPI 0.100.0 and Pydantic v2, use `pattern` instead."
+            ),
+        ] = None,
         examples: Optional[List[Any]] = None,
         example: Annotated[
             Optional[Any],
@@ -264,7 +290,12 @@ class Cookie(Param):
         min_length: Optional[int] = None,
         max_length: Optional[int] = None,
         pattern: Optional[str] = None,
-        regex: Optional[str] = None,
+        regex: Annotated[
+            Optional[str],
+            deprecated(
+                "Deprecated in FastAPI 0.100.0 and Pydantic v2, use `pattern` instead."
+            ),
+        ] = None,
         examples: Optional[List[Any]] = None,
         example: Annotated[
             Optional[Any],
@@ -317,7 +348,12 @@ class Body(FieldInfo):
         min_length: Optional[int] = None,
         max_length: Optional[int] = None,
         pattern: Optional[str] = None,
-        regex: Optional[str] = None,
+        regex: Annotated[
+            Optional[str],
+            deprecated(
+                "Deprecated in FastAPI 0.100.0 and Pydantic v2, use `pattern` instead."
+            ),
+        ] = None,
         examples: Optional[List[Any]] = None,
         example: Annotated[
             Optional[Any],
@@ -334,7 +370,7 @@ class Body(FieldInfo):
             warnings.warn(
                 "`example` has been depreacated, please use `examples` instead",
                 category=DeprecationWarning,
-                stacklevel=1,
+                stacklevel=4,
             )
         self.example = example
         kwargs = dict(
@@ -352,11 +388,16 @@ class Body(FieldInfo):
         )
         if examples is not None:
             kwargs["examples"] = examples
+        if regex is not None:
+            warnings.warn(
+                "`regex` has been depreacated, please use `pattern` instead",
+                category=DeprecationWarning,
+                stacklevel=4,
+            )
         if PYDANTIC_V2:
             kwargs["annotation"] = annotation
             kwargs["pattern"] = pattern or regex
         else:
-            # TODO: pv2 figure out how to deprecate regex
             kwargs["regex"] = pattern or regex
         super().__init__(
             **kwargs,
@@ -383,7 +424,12 @@ class Form(Body):
         min_length: Optional[int] = None,
         max_length: Optional[int] = None,
         pattern: Optional[str] = None,
-        regex: Optional[str] = None,
+        regex: Annotated[
+            Optional[str],
+            deprecated(
+                "Deprecated in FastAPI 0.100.0 and Pydantic v2, use `pattern` instead."
+            ),
+        ] = None,
         examples: Optional[List[Any]] = None,
         example: Annotated[
             Optional[Any],
@@ -433,7 +479,12 @@ class File(Form):
         min_length: Optional[int] = None,
         max_length: Optional[int] = None,
         pattern: Optional[str] = None,
-        regex: Optional[str] = None,
+        regex: Annotated[
+            Optional[str],
+            deprecated(
+                "Deprecated in FastAPI 0.100.0 and Pydantic v2, use `pattern` instead."
+            ),
+        ] = None,
         examples: Optional[List[Any]] = None,
         example: Annotated[
             Optional[Any],
diff --git a/tests/test_regex_deprecated_body.py b/tests/test_regex_deprecated_body.py
new file mode 100644
index 000000000..6384cdd43
--- /dev/null
+++ b/tests/test_regex_deprecated_body.py
@@ -0,0 +1,183 @@
+from typing import Annotated
+
+import pytest
+from dirty_equals import IsDict
+from fastapi import FastAPI, Form
+from fastapi.testclient import TestClient
+from fastapi.utils import match_pydantic_error_url
+
+from .utils import needs_py310
+
+
+def get_client():
+    app = FastAPI()
+    with pytest.warns(DeprecationWarning):
+
+        @app.post("/items/")
+        async def read_items(
+            q: Annotated[str | None, Form(regex="^fixedquery$")] = None
+        ):
+            if q:
+                return f"Hello {q}"
+            else:
+                return "Hello World"
+
+    client = TestClient(app)
+    return client
+
+
+@needs_py310
+def test_no_query():
+    client = get_client()
+    response = client.post("/items/")
+    assert response.status_code == 200
+    assert response.json() == "Hello World"
+
+
+@needs_py310
+def test_q_fixedquery():
+    client = get_client()
+    response = client.post("/items/", data={"q": "fixedquery"})
+    assert response.status_code == 200
+    assert response.json() == "Hello fixedquery"
+
+
+@needs_py310
+def test_query_nonregexquery():
+    client = get_client()
+    response = client.post("/items/", data={"q": "nonregexquery"})
+    assert response.status_code == 422
+    assert response.json() == IsDict(
+        {
+            "detail": [
+                {
+                    "type": "string_pattern_mismatch",
+                    "loc": ["body", "q"],
+                    "msg": "String should match pattern '^fixedquery$'",
+                    "input": "nonregexquery",
+                    "ctx": {"pattern": "^fixedquery$"},
+                    "url": match_pydantic_error_url("string_pattern_mismatch"),
+                }
+            ]
+        }
+    ) | IsDict(
+        # TODO: remove when deprecating Pydantic v1
+        {
+            "detail": [
+                {
+                    "ctx": {"pattern": "^fixedquery$"},
+                    "loc": ["body", "q"],
+                    "msg": 'string does not match regex "^fixedquery$"',
+                    "type": "value_error.str.regex",
+                }
+            ]
+        }
+    )
+
+
+@needs_py310
+def test_openapi_schema():
+    client = get_client()
+    response = client.get("/openapi.json")
+    assert response.status_code == 200, response.text
+    # insert_assert(response.json())
+    assert response.json() == {
+        "openapi": "3.1.0",
+        "info": {"title": "FastAPI", "version": "0.1.0"},
+        "paths": {
+            "/items/": {
+                "post": {
+                    "summary": "Read Items",
+                    "operationId": "read_items_items__post",
+                    "requestBody": {
+                        "content": {
+                            "application/x-www-form-urlencoded": {
+                                "schema": IsDict(
+                                    {
+                                        "allOf": [
+                                            {
+                                                "$ref": "#/components/schemas/Body_read_items_items__post"
+                                            }
+                                        ],
+                                        "title": "Body",
+                                    }
+                                )
+                                | IsDict(
+                                    # TODO: remove when deprecating Pydantic v1
+                                    {
+                                        "$ref": "#/components/schemas/Body_read_items_items__post"
+                                    }
+                                )
+                            }
+                        }
+                    },
+                    "responses": {
+                        "200": {
+                            "description": "Successful Response",
+                            "content": {"application/json": {"schema": {}}},
+                        },
+                        "422": {
+                            "description": "Validation Error",
+                            "content": {
+                                "application/json": {
+                                    "schema": {
+                                        "$ref": "#/components/schemas/HTTPValidationError"
+                                    }
+                                }
+                            },
+                        },
+                    },
+                }
+            }
+        },
+        "components": {
+            "schemas": {
+                "Body_read_items_items__post": {
+                    "properties": {
+                        "q": IsDict(
+                            {
+                                "anyOf": [
+                                    {"type": "string", "pattern": "^fixedquery$"},
+                                    {"type": "null"},
+                                ],
+                                "title": "Q",
+                            }
+                        )
+                        | IsDict(
+                            # TODO: remove when deprecating Pydantic v1
+                            {"type": "string", "pattern": "^fixedquery$", "title": "Q"}
+                        )
+                    },
+                    "type": "object",
+                    "title": "Body_read_items_items__post",
+                },
+                "HTTPValidationError": {
+                    "properties": {
+                        "detail": {
+                            "items": {"$ref": "#/components/schemas/ValidationError"},
+                            "type": "array",
+                            "title": "Detail",
+                        }
+                    },
+                    "type": "object",
+                    "title": "HTTPValidationError",
+                },
+                "ValidationError": {
+                    "properties": {
+                        "loc": {
+                            "items": {
+                                "anyOf": [{"type": "string"}, {"type": "integer"}]
+                            },
+                            "type": "array",
+                            "title": "Location",
+                        },
+                        "msg": {"type": "string", "title": "Message"},
+                        "type": {"type": "string", "title": "Error Type"},
+                    },
+                    "type": "object",
+                    "required": ["loc", "msg", "type"],
+                    "title": "ValidationError",
+                },
+            }
+        },
+    }
diff --git a/tests/test_regex_deprecated_params.py b/tests/test_regex_deprecated_params.py
new file mode 100644
index 000000000..5ea4f2ada
--- /dev/null
+++ b/tests/test_regex_deprecated_params.py
@@ -0,0 +1,166 @@
+from typing import Annotated
+
+import pytest
+from dirty_equals import IsDict
+from fastapi import FastAPI, Query
+from fastapi.testclient import TestClient
+from fastapi.utils import match_pydantic_error_url
+
+from .utils import needs_py310
+
+
+def get_client():
+    app = FastAPI()
+    with pytest.warns(DeprecationWarning):
+
+        @app.get("/items/")
+        async def read_items(
+            q: Annotated[str | None, Query(regex="^fixedquery$")] = None
+        ):
+            if q:
+                return f"Hello {q}"
+            else:
+                return "Hello World"
+
+    client = TestClient(app)
+    return client
+
+
+@needs_py310
+def test_query_params_str_validations_no_query():
+    client = get_client()
+    response = client.get("/items/")
+    assert response.status_code == 200
+    assert response.json() == "Hello World"
+
+
+@needs_py310
+def test_query_params_str_validations_q_fixedquery():
+    client = get_client()
+    response = client.get("/items/", params={"q": "fixedquery"})
+    assert response.status_code == 200
+    assert response.json() == "Hello fixedquery"
+
+
+@needs_py310
+def test_query_params_str_validations_item_query_nonregexquery():
+    client = get_client()
+    response = client.get("/items/", params={"q": "nonregexquery"})
+    assert response.status_code == 422
+    assert response.json() == IsDict(
+        {
+            "detail": [
+                {
+                    "type": "string_pattern_mismatch",
+                    "loc": ["query", "q"],
+                    "msg": "String should match pattern '^fixedquery$'",
+                    "input": "nonregexquery",
+                    "ctx": {"pattern": "^fixedquery$"},
+                    "url": match_pydantic_error_url("string_pattern_mismatch"),
+                }
+            ]
+        }
+    ) | IsDict(
+        # TODO: remove when deprecating Pydantic v1
+        {
+            "detail": [
+                {
+                    "ctx": {"pattern": "^fixedquery$"},
+                    "loc": ["query", "q"],
+                    "msg": 'string does not match regex "^fixedquery$"',
+                    "type": "value_error.str.regex",
+                }
+            ]
+        }
+    )
+
+
+@needs_py310
+def test_openapi_schema():
+    client = get_client()
+    response = client.get("/openapi.json")
+    assert response.status_code == 200, response.text
+    # insert_assert(response.json())
+    assert response.json() == {
+        "openapi": "3.1.0",
+        "info": {"title": "FastAPI", "version": "0.1.0"},
+        "paths": {
+            "/items/": {
+                "get": {
+                    "summary": "Read Items",
+                    "operationId": "read_items_items__get",
+                    "parameters": [
+                        {
+                            "name": "q",
+                            "in": "query",
+                            "required": False,
+                            "schema": IsDict(
+                                {
+                                    "anyOf": [
+                                        {"type": "string", "pattern": "^fixedquery$"},
+                                        {"type": "null"},
+                                    ],
+                                    "title": "Q",
+                                }
+                            )
+                            | IsDict(
+                                # TODO: remove when deprecating Pydantic v1
+                                {
+                                    "type": "string",
+                                    "pattern": "^fixedquery$",
+                                    "title": "Q",
+                                }
+                            ),
+                        }
+                    ],
+                    "responses": {
+                        "200": {
+                            "description": "Successful Response",
+                            "content": {"application/json": {"schema": {}}},
+                        },
+                        "422": {
+                            "description": "Validation Error",
+                            "content": {
+                                "application/json": {
+                                    "schema": {
+                                        "$ref": "#/components/schemas/HTTPValidationError"
+                                    }
+                                }
+                            },
+                        },
+                    },
+                }
+            }
+        },
+        "components": {
+            "schemas": {
+                "HTTPValidationError": {
+                    "properties": {
+                        "detail": {
+                            "items": {"$ref": "#/components/schemas/ValidationError"},
+                            "type": "array",
+                            "title": "Detail",
+                        }
+                    },
+                    "type": "object",
+                    "title": "HTTPValidationError",
+                },
+                "ValidationError": {
+                    "properties": {
+                        "loc": {
+                            "items": {
+                                "anyOf": [{"type": "string"}, {"type": "integer"}]
+                            },
+                            "type": "array",
+                            "title": "Location",
+                        },
+                        "msg": {"type": "string", "title": "Message"},
+                        "type": {"type": "string", "title": "Error Type"},
+                    },
+                    "type": "object",
+                    "required": ["loc", "msg", "type"],
+                    "title": "ValidationError",
+                },
+            }
+        },
+    }