diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 815617e1c19..6d0c8a2aa41 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -82,7 +82,7 @@ jobs:
       - run: pip install nox
       - run: nox -s prepare-release -- 99.9
       - run: nox -s build-release -- 99.9
-      - run: pipx run check-manifest
+      - run: pipx run check-sdist
 
   vendoring:
     name: vendoring
diff --git a/MANIFEST.in b/MANIFEST.in
deleted file mode 100644
index 998cb4f485e..00000000000
--- a/MANIFEST.in
+++ /dev/null
@@ -1,34 +0,0 @@
-include NEWS.rst
-include README.rst
-include SECURITY.md
-include pyproject.toml
-
-include build-project/build-requirements.in
-include build-project/build-requirements.txt
-include build-project/build-project.py
-include build-project/.python-version
-
-include src/pip/_vendor/README.rst
-include src/pip/_vendor/vendor.txt
-
-include docs/requirements.txt
-
-exclude .git-blame-ignore-revs
-exclude .mailmap
-exclude .readthedocs.yml
-exclude .pre-commit-config.yaml
-exclude .readthedocs-custom-redirects.yml
-exclude noxfile.py
-
-recursive-include src/pip/_vendor *.pem
-recursive-include src/pip/_vendor py.typed
-recursive-include docs *.css *.py *.rst *.md
-recursive-include docs *.dot *.png
-
-recursive-exclude src/pip/_vendor *.pyi
-
-prune .github
-prune docs/build
-prune news
-prune tests
-prune tools
diff --git a/build-project/build-requirements.in b/build-project/build-requirements.in
index 4bc215a28d0..07a76cea647 100644
--- a/build-project/build-requirements.in
+++ b/build-project/build-requirements.in
@@ -1,2 +1,2 @@
 build
-setuptools
+flit-core
diff --git a/build-project/build-requirements.txt b/build-project/build-requirements.txt
index c0cf0575088..65b647daf2c 100644
--- a/build-project/build-requirements.txt
+++ b/build-project/build-requirements.txt
@@ -8,17 +8,15 @@ build==1.2.2.post1 \
     --hash=sha256:1d61c0887fa860c01971625baae8bdd338e517b836a2f70dd1f7aa3a6b2fc5b5 \
     --hash=sha256:b36993e92ca9375a219c99e606a122ff365a760a2d4bba0caa09bd5278b608b7
     # via -r build-requirements.in
-packaging==24.2 \
-    --hash=sha256:09abb1bccd265c01f4a3aa3f7a7db064b36514d2cba19a2f694fe6150451a759 \
-    --hash=sha256:c228a6dc5e932d346bc5739379109d49e8853dd8223571c7c5b55260edc0b97f
+flit-core==3.12.0 \
+    --hash=sha256:18f63100d6f94385c6ed57a72073443e1a71a4acb4339491615d0f16d6ff01b2 \
+    --hash=sha256:e7a0304069ea895172e3c7bb703292e992c5d1555dd1233ab7b5621b5b69e62c
+    # via -r build-requirements.in
+packaging==25.0 \
+    --hash=sha256:29572ef2b1f17581046b3a2227d5c611fb25ec70ca1ba8554b24b0e69331a484 \
+    --hash=sha256:d443872c98d677bf60f6a1f2f8c1cb748e8fe762d2bf9d3148b5599295b0fc4f
     # via build
 pyproject-hooks==1.2.0 \
     --hash=sha256:1e859bd5c40fae9448642dd871adf459e5e2084186e8d2c2a79a824c970da1f8 \
     --hash=sha256:9e5c6bfa8dcc30091c74b0cf803c81fdd29d94f01992a7707bc97babb1141913
     # via build
-
-# The following packages are considered to be unsafe in a requirements file:
-setuptools==80.9.0 \
-    --hash=sha256:062d34222ad13e0cc312a4c02d73f059e86a4acbfbdea8f8f76b28c99f306922 \
-    --hash=sha256:f36b47402ecde768dbfafc46e8e4207b4360c654f1f3bb84475f0a28628fb19c
-    # via -r build-requirements.in
diff --git a/docs/html/development/architecture/anatomy.rst b/docs/html/development/architecture/anatomy.rst
index d5e205654ff..7a0fefbfa63 100644
--- a/docs/html/development/architecture/anatomy.rst
+++ b/docs/html/development/architecture/anatomy.rst
@@ -18,7 +18,6 @@ The ``README``, license, ``pyproject.toml``, and so on are in the top level.
 
 * ``AUTHORS.txt``
 * ``LICENSE.txt``
-* ``MANIFEST.in``
 * ``NEWS.rst``
 * ``pyproject.toml``
 * ``README.rst``
diff --git a/news/13743.feature.rst b/news/13743.feature.rst
new file mode 100644
index 00000000000..37f7db147f8
--- /dev/null
+++ b/news/13743.feature.rst
@@ -0,0 +1,2 @@
+Building pip itself from source now uses flit-core instead of setuptools.
+This does not affect how pip installs or builds packages you use.
diff --git a/pyproject.toml b/pyproject.toml
index 90f04307f47..8f7b03813a2 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -1,6 +1,5 @@
 [project]
 dynamic = ["version"]
-
 name = "pip"
 description = "The PyPA recommended tool for installing Python packages."
 readme = "README.rst"
@@ -45,12 +44,13 @@ Source = "https://github.com/pypa/pip"
 Changelog = "https://pip.pypa.io/en/stable/news/"
 
 [build-system]
-requires = ["setuptools>=77"]
-build-backend = "setuptools.build_meta"
+requires = ["flit-core >=3.11,<4"]
+build-backend = "flit_core.buildapi"
 
 [dependency-groups]
 test = [
     "cryptography",
+    "flit-core >= 3.11, < 4",
     "freezegun",
     "installer",
     "pytest",
@@ -70,6 +70,7 @@ test = [
 ]
 
 test-common-wheels = [
+    "flit-core >= 3.11, < 4",
     # We pin setuptools<80 because our test suite currently
     # depends on setup.py develop to generate egg-link files.
     "setuptools >= 40.8.0, != 60.6.0, <80",
@@ -78,28 +79,24 @@ test-common-wheels = [
     "coverage >= 4.4",
 ]
 
-[tool.setuptools]
-package-dir = {"" = "src"}
-include-package-data = false
-
-[tool.setuptools.dynamic]
-version = {attr = "pip.__version__"}
-
-[tool.setuptools.packages.find]
-where = ["src"]
-exclude = ["contrib", "docs", "tests*", "tasks"]
-
-[tool.setuptools.package-data]
-"pip" = ["py.typed"]
-"pip._vendor" = ["vendor.txt"]
-"pip._vendor.certifi" = ["*.pem"]
-"pip._vendor.distlib" = [
-    "t32.exe",
-    "t64.exe",
-    "t64-arm.exe",
-    "w32.exe",
-    "w64.exe",
-    "w64-arm.exe",
+[tool.flit.sdist]
+include = [
+    "NEWS.rst",
+    "SECURITY.md",
+    "build-project/.python-version",
+    "build-project/build-project.py",
+    "build-project/build-requirements.in",
+    "build-project/build-requirements.txt",
+    "docs/requirements.txt",
+    "docs/**/*.css",
+    "docs/**/*.dot",
+    "docs/**/*.md",
+    "docs/**/*.png",
+    "docs/**/*.py",
+    "docs/**/*.rst",
+]
+exclude = [
+    "src/pip/_vendor/**/*.pyi",
 ]
 
 ######################################################################################
@@ -350,3 +347,15 @@ exclude_also = [
     # This excludes typing-specific code, which will be validated by mypy anyway.
     "if TYPE_CHECKING",
 ]
+
+[tool.check-sdist]
+git-only = [
+  "tests/**",
+  "tools/**",
+  "news/.gitignore",
+  ".gitattributes",
+  ".gitignore",
+  ".git-blame-ignore-revs",
+  ".mailmap",
+  ".readthedocs-custom-redirects.yml"
+]
diff --git a/tests/functional/test_freeze.py b/tests/functional/test_freeze.py
index 0a7cedd11cb..9883beb87fd 100644
--- a/tests/functional/test_freeze.py
+++ b/tests/functional/test_freeze.py
@@ -99,38 +99,33 @@ def test_freeze_with_pip(script: PipTestEnvironment) -> None:
 
 def test_freeze_with_setuptools(script: PipTestEnvironment) -> None:
     """
-    Test that pip shows setuptools only when --all is used
-    or _should_suppress_build_backends() returns false
+    Test that pip shows setuptools only when --all is used on Python < 3.12,
+    otherwise it should be shown in default freeze output.
     """
 
     result = script.pip("freeze", "--all")
     assert "setuptools==" in result.stdout
 
-    (script.site_packages_path / "mock.pth").write_text("import mock\n")
-
-    (script.site_packages_path / "mock.py").write_text(
-        textwrap.dedent(
-            """\
-                import pip._internal.commands.freeze as freeze
-                freeze._should_suppress_build_backends = lambda: False
-            """
-        )
-    )
-
+    # Test the default behavior (without --all)
     result = script.pip("freeze")
-    assert "setuptools==" in result.stdout
 
-    (script.site_packages_path / "mock.py").write_text(
-        textwrap.dedent(
-            """\
-                import pip._internal.commands.freeze as freeze
-                freeze._should_suppress_build_backends = lambda: True
-            """
+    should_suppress = sys.version_info < (3, 12)
+    if should_suppress:
+        # setuptools should be hidden in default freeze output
+        assert "setuptools==" not in result.stdout, (
+            f"setuptools should be suppressed in Python {sys.version_info[:2]} "
+            f"but was found in freeze output: {result.stdout}"
+        )
+    else:
+        # setuptools should be shown in default freeze output
+        assert "setuptools==" in result.stdout, (
+            f"setuptools should be shown in Python {sys.version_info[:2]} "
+            f"but was not found in freeze output: {result.stdout}"
         )
-    )
 
-    result = script.pip("freeze")
-    assert "setuptools==" not in result.stdout
+    # --all should always show setuptools regardless of version
+    result_all = script.pip("freeze", "--all")
+    assert "setuptools==" in result_all.stdout
 
 
 def test_exclude_and_normalization(script: PipTestEnvironment, tmpdir: Path) -> None:
diff --git a/tests/functional/test_self_update.py b/tests/functional/test_self_update.py
index 1331a87c319..9019e89211d 100644
--- a/tests/functional/test_self_update.py
+++ b/tests/functional/test_self_update.py
@@ -8,6 +8,9 @@ def test_self_update_editable(script: Any, pip_src: Any) -> None:
     # mode, that pip can safely update itself to an editable install.
     # See https://github.com/pypa/pip/issues/12666 for details.
 
+    # Install flit-core (build backend) since we use --no-build-isolation
+    script.pip("install", "flit-core")
+
     # Step 1. Install pip as non-editable. This is expected to succeed as
     # the existing pip in the environment is installed in editable mode, so
     # it only places a .pth file in the environment.