diff --git a/.changeset/raise_minimum_httpx_version_to_0231.md b/.changeset/raise_minimum_httpx_version_to_0231.md
@@ -0,0 +1,5 @@
+---
+default: major
+---
+
+# Raise minimum httpx version to 0.23.1
diff --git a/end_to_end_tests/docstrings-on-attributes-golden-record/pyproject.toml b/end_to_end_tests/docstrings-on-attributes-golden-record/pyproject.toml
@@ -11,7 +11,7 @@ include = ["my_test_api_client/py.typed"]
 
 [tool.poetry.dependencies]
 python = "^3.10"
-httpx = ">=0.23.0,<0.29.0"
+httpx = ">=0.23.1,<0.29.0"
 attrs = ">=22.2.0"
 
 [build-system]

diff --git a/end_to_end_tests/golden-record/my_test_api_client/api/bodies/post_bodies_multiple.py b/end_to_end_tests/golden-record/my_test_api_client/api/bodies/post_bodies_multiple.py
@@ -30,18 +30,16 @@ def _get_kwargs(
     if isinstance(body, File):
         if not isinstance(body, Unset):
             _kwargs["content"] = body.payload
-
         headers["Content-Type"] = "application/octet-stream"
     if isinstance(body, PostBodiesMultipleDataBody):
         if not isinstance(body, Unset):
             _kwargs["data"] = body.to_dict()
-
         headers["Content-Type"] = "application/x-www-form-urlencoded"
     if isinstance(body, PostBodiesMultipleFilesBody):
         if not isinstance(body, Unset):
             _kwargs["files"] = body.to_multipart()
 
-        headers["Content-Type"] = "multipart/form-data"
+        headers["Content-Type"] = "multipart/form-data; boundary=+++"
 
     _kwargs["headers"] = headers
     return _kwargs

diff --git a/..._tests/golden-record/my_test_api_client/api/tests/octet_stream_tests_octet_stream_post.py b/..._tests/golden-record/my_test_api_client/api/tests/octet_stream_tests_octet_stream_post.py
@@ -23,7 +23,6 @@ def _get_kwargs(
 
     if not isinstance(body, Unset):
         _kwargs["content"] = body.payload
-
     headers["Content-Type"] = "application/octet-stream"
 
     _kwargs["headers"] = headers

diff --git a/end_to_end_tests/golden-record/my_test_api_client/api/tests/post_form_data.py b/end_to_end_tests/golden-record/my_test_api_client/api/tests/post_form_data.py
@@ -21,7 +21,6 @@ def _get_kwargs(
     }
 
     _kwargs["data"] = body.to_dict()
-
     headers["Content-Type"] = "application/x-www-form-urlencoded"
 
     _kwargs["headers"] = headers

diff --git a/end_to_end_tests/golden-record/my_test_api_client/api/tests/post_form_data_inline.py b/end_to_end_tests/golden-record/my_test_api_client/api/tests/post_form_data_inline.py
@@ -21,7 +21,6 @@ def _get_kwargs(
     }
 
     _kwargs["data"] = body.to_dict()
-
     headers["Content-Type"] = "application/x-www-form-urlencoded"
 
     _kwargs["headers"] = headers

diff --git a/end_to_end_tests/golden-record/my_test_api_client/api/tests/upload_file_tests_upload_post.py b/end_to_end_tests/golden-record/my_test_api_client/api/tests/upload_file_tests_upload_post.py
@@ -23,6 +23,8 @@ def _get_kwargs(
 
     _kwargs["files"] = body.to_multipart()
 
+    headers["Content-Type"] = "multipart/form-data; boundary=+++"
+
     _kwargs["headers"] = headers
     return _kwargs
 

diff --git a/end_to_end_tests/golden-record/pyproject.toml b/end_to_end_tests/golden-record/pyproject.toml
@@ -11,7 +11,7 @@ include = ["my_test_api_client/py.typed"]
 
 [tool.poetry.dependencies]
 python = "^3.10"
-httpx = ">=0.23.0,<0.29.0"
+httpx = ">=0.23.1,<0.29.0"
 attrs = ">=22.2.0"
 
 [build-system]

diff --git a/end_to_end_tests/literal-enums-golden-record/my_enum_api_client/api/tests/post_user_list.py b/end_to_end_tests/literal-enums-golden-record/my_enum_api_client/api/tests/post_user_list.py
@@ -24,6 +24,8 @@ def _get_kwargs(
     if not isinstance(body, Unset):
         _kwargs["files"] = body.to_multipart()
 
+    headers["Content-Type"] = "multipart/form-data; boundary=+++"
+
     _kwargs["headers"] = headers
     return _kwargs
 

diff --git a/end_to_end_tests/literal-enums-golden-record/pyproject.toml b/end_to_end_tests/literal-enums-golden-record/pyproject.toml
@@ -11,7 +11,7 @@ include = ["my_enum_api_client/py.typed"]
 
 [tool.poetry.dependencies]
 python = "^3.10"
-httpx = ">=0.23.0,<0.29.0"
+httpx = ">=0.23.1,<0.29.0"
 attrs = ">=22.2.0"
 
 [build-system]

diff --git a/end_to_end_tests/metadata_snapshots/pdm.pyproject.toml b/end_to_end_tests/metadata_snapshots/pdm.pyproject.toml
@@ -6,7 +6,7 @@ authors = []
 readme = "README.md"
 requires-python = ">=3.10"
 dependencies = [
-    "httpx>=0.23.0,<0.29.0",
+    "httpx>=0.23.1,<0.29.0",
     "attrs>=22.2.0",
 ]
 

diff --git a/end_to_end_tests/metadata_snapshots/poetry.pyproject.toml b/end_to_end_tests/metadata_snapshots/poetry.pyproject.toml
@@ -11,7 +11,7 @@ include = ["test_3_1_features_client/py.typed"]
 
 [tool.poetry.dependencies]
 python = "^3.10"
-httpx = ">=0.23.0,<0.29.0"
+httpx = ">=0.23.1,<0.29.0"
 attrs = ">=22.2.0"
 
 [build-system]

diff --git a/end_to_end_tests/metadata_snapshots/setup.py b/end_to_end_tests/metadata_snapshots/setup.py
@@ -13,6 +13,6 @@
     long_description_content_type="text/markdown",
     packages=find_packages(),
     python_requires=">=3.10, <4",
-    install_requires=["httpx >= 0.23.0, < 0.29.0", "attrs >= 22.2.0"],
+    install_requires=["httpx >= 0.23.1, < 0.29.0", "attrs >= 22.2.0"],
     package_data={"test_3_1_features_client": ["py.typed"]},
 )
diff --git a/end_to_end_tests/metadata_snapshots/uv.pyproject.toml b/end_to_end_tests/metadata_snapshots/uv.pyproject.toml
@@ -6,7 +6,7 @@ authors = []
 requires-python = ">=3.10"
 readme = "README.md"
 dependencies = [
-    "httpx>=0.23.0,<0.29.0",
+    "httpx>=0.23.1,<0.29.0",
     "attrs>=22.2.0",
 ]
 

diff --git a/end_to_end_tests/test-3-1-golden-record/pyproject.toml b/end_to_end_tests/test-3-1-golden-record/pyproject.toml
@@ -11,7 +11,7 @@ include = ["test_3_1_features_client/py.typed"]
 
 [tool.poetry.dependencies]
 python = "^3.10"
-httpx = ">=0.23.0,<0.29.0"
+httpx = ">=0.23.1,<0.29.0"
 attrs = ">=22.2.0"
 
 [build-system]

diff --git a/integration-tests/integration_tests/api/body/post_body_multipart.py b/integration-tests/integration_tests/api/body/post_body_multipart.py
@@ -25,6 +25,8 @@ def _get_kwargs(
     if not isinstance(body, Unset):
         _kwargs["files"] = body.to_multipart()
 
+    headers["Content-Type"] = "multipart/form-data; boundary=+++"
+
     _kwargs["headers"] = headers
     return _kwargs
 

diff --git a/integration-tests/pdm.minimal.lock b/integration-tests/pdm.minimal.lock
@@ -5,26 +5,25 @@
 groups = ["default", "dev"]
 strategy = ["direct_minimal_versions", "inherit_metadata"]
 lock_version = "4.5.0"
-content_hash = "sha256:70373f7c996c7e4f5c163216d115b5037e5a03f4bbe72963dd4482c84ff5410b"
+content_hash = "sha256:eeb709f45e01d5d34a3c94a4a0b8b9bfdc61c6c2ddeebe1a4462e69c6ea8ad39"
 
 [[metadata.targets]]
 requires_python = "~=3.10"
 
 [[package]]
 name = "anyio"
-version = "3.7.1"
-requires_python = ">=3.7"
-summary = "High level compatibility layer for multiple asynchronous event loop implementations"
+version = "4.13.0"
+requires_python = ">=3.10"
+summary = "High-level concurrency and networking framework on top of asyncio or Trio"
 groups = ["default"]
 dependencies = [
-    "exceptiongroup; python_version < \"3.11\"",
+    "exceptiongroup>=1.0.2; python_version < \"3.11\"",
     "idna>=2.8",
-    "sniffio>=1.1",
-    "typing-extensions; python_version < \"3.8\"",
+    "typing-extensions>=4.5; python_version < \"3.13\"",
 ]
 files = [
-    {file = "anyio-3.7.1-py3-none-any.whl", hash = "sha256:91dee416e570e92c64041bd18b900d1d6fa78dff7048769ce5ac5ddad004fbb5"},
-    {file = "anyio-3.7.1.tar.gz", hash = "sha256:44a3c9aba0f5defa43261a8b3efb97891f2bd7d804e0e1f56419befa1adfc780"},
+    {file = "anyio-4.13.0-py3-none-any.whl", hash = "sha256:08b310f9e24a9594186fd75b4f73f4a4152069e3853f1ed8bfbf58369f4ad708"},
+    {file = "anyio-4.13.0.tar.gz", hash = "sha256:334b70e641fd2221c1505b3890c69882fe4a2df910cba14d97019b90b24439dc"},
 ]
 
 [[package]]
@@ -78,58 +77,61 @@ files = [
 
 [[package]]
 name = "h11"
-version = "0.12.0"
-requires_python = ">=3.6"
+version = "0.14.0"
+requires_python = ">=3.7"
 summary = "A pure-Python, bring-your-own-I/O implementation of HTTP/1.1"
 groups = ["default"]
+dependencies = [
+    "typing-extensions; python_version < \"3.8\"",
+]
 files = [
-    {file = "h11-0.12.0-py3-none-any.whl", hash = "sha256:36a3cb8c0a032f56e2da7084577878a035d3b61d104230d4bd49c0c6b555a9c6"},
-    {file = "h11-0.12.0.tar.gz", hash = "sha256:47222cb6067e4a307d535814917cd98fd0a57b6788ce715755fa2b6c28b56042"},
+    {file = "h11-0.14.0-py3-none-any.whl", hash = "sha256:e3fe4ac4b851c468cc8363d500db52c2ead036020723024a109d37346efaa761"},
+    {file = "h11-0.14.0.tar.gz", hash = "sha256:8f19fbbe99e72420ff35c00b27a34cb9937e902a8b810e2c88300c6f0a3b699d"},
 ]
 
 [[package]]
 name = "httpcore"
-version = "0.15.0"
+version = "0.16.3"
 requires_python = ">=3.7"
 summary = "A minimal low-level HTTP client."
 groups = ["default"]
 dependencies = [
-    "anyio==3.*",
+    "anyio<5.0,>=3.0",
     "certifi",
-    "h11<0.13,>=0.11",
+    "h11<0.15,>=0.13",
     "sniffio==1.*",
 ]
 files = [
-    {file = "httpcore-0.15.0-py3-none-any.whl", hash = "sha256:1105b8b73c025f23ff7c36468e4432226cbb959176eab66864b8e31c4ee27fa6"},
-    {file = "httpcore-0.15.0.tar.gz", hash = "sha256:18b68ab86a3ccf3e7dc0f43598eaddcf472b602aba29f9aa6ab85fe2ada3980b"},
+    {file = "httpcore-0.16.3-py3-none-any.whl", hash = "sha256:da1fb708784a938aa084bde4feb8317056c55037247c787bd7e19eb2c2949dc0"},
+    {file = "httpcore-0.16.3.tar.gz", hash = "sha256:c5d6f04e2fc530f39e0c077e6a30caa53f1451096120f1f38b954afd0b17c0cb"},
 ]
 
 [[package]]
 name = "httpx"
-version = "0.23.0"
+version = "0.23.1"
 requires_python = ">=3.7"
 summary = "The next generation HTTP client."
 groups = ["default"]
 dependencies = [
     "certifi",
-    "httpcore<0.16.0,>=0.15.0",
+    "httpcore<0.17.0,>=0.15.0",
     "rfc3986[idna2008]<2,>=1.3",
     "sniffio",
 ]
 files = [
-    {file = "httpx-0.23.0-py3-none-any.whl", hash = "sha256:42974f577483e1e932c3cdc3cd2303e883cbfba17fe228b0f63589764d7b9c4b"},
-    {file = "httpx-0.23.0.tar.gz", hash = "sha256:f28eac771ec9eb4866d3fb4ab65abd42d38c424739e80c08d8d20570de60b0ef"},
+    {file = "httpx-0.23.1-py3-none-any.whl", hash = "sha256:0b9b1f0ee18b9978d637b0776bfd7f54e2ca278e063e3586d8f01cda89e042a8"},
+    {file = "httpx-0.23.1.tar.gz", hash = "sha256:202ae15319be24efe9a8bd4ed4360e68fde7b38bcc2ce87088d416f026667d19"},
 ]
 
 [[package]]
 name = "idna"
-version = "3.16"
+version = "3.17"
 requires_python = ">=3.9"
 summary = "Internationalized Domain Names in Applications (IDNA)"
 groups = ["default"]
 files = [
-    {file = "idna-3.16-py3-none-any.whl", hash = "sha256:cc246e3a3f89580c3a951b5ad298ca4638078b2cdd4f115654332b5c26daded5"},
-    {file = "idna-3.16.tar.gz", hash = "sha256:d7a6da03db833450fca25d2358ac9ff06cd624577a4aea3a596d5c0f77b8e03d"},
+    {file = "idna-3.17-py3-none-any.whl", hash = "sha256:466e48829084efe2548012b855df21540b96f2e20e51bd124c851536556a592c"},
+    {file = "idna-3.17.tar.gz", hash = "sha256:5eb0cb53bc467c12eadcf6de83163ad8527cec9416f44b9b61b19caedad2b87f"},
 ]
 
 [[package]]

diff --git a/integration-tests/pyproject.toml b/integration-tests/pyproject.toml
@@ -6,7 +6,7 @@ authors = []
 readme = "README.md"
 requires-python = ">=3.10,<4.0"
 dependencies = [
-    "httpx>=0.23.0,<0.29.0",
+    "httpx>=0.23.1,<0.29.0",
     "attrs>=22.2.0",
 ]
 

diff --git a/openapi_python_client/templates/endpoint_module.py.jinja b/openapi_python_client/templates/endpoint_module.py.jinja
@@ -50,12 +50,18 @@ def _get_kwargs(
 {% for body in endpoint.bodies %}
     if isinstance(body, {{body.prop.get_type_string(no_optional=True) }}):
         {{ body_to_kwarg(body) | indent(8) }}
+        {%- if body.content_type == "multipart/form-data" %}
+        headers["Content-Type"] = "multipart/form-data; boundary=+++"
+        {% else %}
         headers["Content-Type"] = "{{ body.content_type }}"
+        {% endif %}
 {% endfor %}
 {% elif endpoint.bodies | length == 1 %}
 {% set body = endpoint.bodies[0] %}
     {{ body_to_kwarg(body) | indent(4) }}
-    {% if body.content_type != "multipart/form-data" %}{# Need httpx to set the boundary automatically #}
+    {%- if body.content_type == "multipart/form-data" %}
+    headers["Content-Type"] = "multipart/form-data; boundary=+++"
+    {% else %}
     headers["Content-Type"] = "{{ body.content_type }}"
     {% endif %}
 {% endif %}

diff --git a/openapi_python_client/templates/pyproject_pdm.toml.jinja b/openapi_python_client/templates/pyproject_pdm.toml.jinja
@@ -6,7 +6,7 @@ authors = []
 readme = "README.md"
 requires-python = ">=3.10"
 dependencies = [
-    "httpx>=0.23.0,<0.29.0",
+    "httpx>=0.23.1,<0.29.0",
     "attrs>=22.2.0",
 ]
 

diff --git a/openapi_python_client/templates/pyproject_poetry.toml.jinja b/openapi_python_client/templates/pyproject_poetry.toml.jinja
@@ -11,7 +11,7 @@ include = ["{{ package_name }}/py.typed"]
 
 [tool.poetry.dependencies]
 python = "^3.10"
-httpx = ">=0.23.0,<0.29.0"
+httpx = ">=0.23.1,<0.29.0"
 attrs = ">=22.2.0"
 
 [build-system]

diff --git a/openapi_python_client/templates/pyproject_uv.toml.jinja b/openapi_python_client/templates/pyproject_uv.toml.jinja
@@ -6,7 +6,7 @@ authors = []
 requires-python = ">=3.10"
 readme = "README.md"
 dependencies = [
-    "httpx>=0.23.0,<0.29.0",
+    "httpx>=0.23.1,<0.29.0",
     "attrs>=22.2.0",
 ]
 

diff --git a/openapi_python_client/templates/setup.py.jinja b/openapi_python_client/templates/setup.py.jinja
@@ -13,6 +13,6 @@ setup(
     long_description_content_type="text/markdown",
     packages=find_packages(),
     python_requires=">=3.10, <4",
-    install_requires=["httpx >= 0.23.0, < 0.29.0", "attrs >= 22.2.0"],
+    install_requires=["httpx >= 0.23.1, < 0.29.0", "attrs >= 22.2.0"],
     package_data={"{{ package_name }}": ["py.typed"]},
 )
-Original file line number
+Diff line change
@@ Expand Up / @@ -21,7 +21,6 @@ def _get_kwargs( @@
         }
         _kwargs["data"] = body.to_dict()
         headers["Content-Type"] = "application/x-www-form-urlencoded"
         _kwargs["headers"] = headers
@@ Expand Down @@