diff --git a/.github/workflows/check.yaml b/.github/workflows/check.yaml
index 20ad76a..92f2550 100644
--- a/.github/workflows/check.yaml
+++ b/.github/workflows/check.yaml
@@ -19,6 +19,8 @@ jobs:
       fail-fast: false
       matrix:
         env:
+          - "3.15"
+          - "3.15t"
           - "3.14"
           - "3.13"
           - "3.12"
diff --git a/docs/changelog/104.packaging.rst b/docs/changelog/104.packaging.rst
new file mode 100644
index 0000000..3206810
--- /dev/null
+++ b/docs/changelog/104.packaging.rst
@@ -0,0 +1 @@
+Declare support for Python 3.15 and run the test suite against it, currently in beta.
diff --git a/pyproject.toml b/pyproject.toml
index bdfede7..f4a0b14 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -35,6 +35,7 @@ classifiers = [
   "Programming Language :: Python :: 3.12",
   "Programming Language :: Python :: 3.13",
   "Programming Language :: Python :: 3.14",
+  "Programming Language :: Python :: 3.15",
   "Programming Language :: Python :: Implementation :: CPython",
   "Topic :: Software Development :: Libraries",
   "Topic :: Utilities",
@@ -145,7 +146,7 @@ write-changes = true
 count = true
 
 [tool.pyproject-fmt]
-max_supported_python = "3.14"
+max_supported_python = "3.15"
 
 [tool.ty]
 src.exclude = [ "tests/windows/winreg_mock_values.py" ]
diff --git a/tests/test_discovery.py b/tests/test_discovery.py
index 9ea5ab4..138650d 100644
--- a/tests/test_discovery.py
+++ b/tests/test_discovery.py
@@ -437,7 +437,8 @@ def reject_first(info: PythonInfo) -> bool:
         proposed.append(str(info.executable))
         return len(proposed) > 1
 
-    result = get_interpreter([f"{major}.{minor}", sys.executable], [], session_cache, predicate=reject_first)
+    threaded = "t" if current.free_threaded else ""
+    result = get_interpreter([f"{major}.{minor}{threaded}", sys.executable], [], session_cache, predicate=reject_first)
     # rejecting the first proposal must not abort discovery; a later proposal (same or fallback spec) is accepted -
     # on hosts where every alias resolves to one interpreter the fallback re-proposes it, so executables may match
     assert result is not None
diff --git a/tests/test_py_info_extra.py b/tests/test_py_info_extra.py
index 19b5685..6cdebf1 100644
--- a/tests/test_py_info_extra.py
+++ b/tests/test_py_info_extra.py
@@ -437,7 +437,10 @@ def test_satisfies_version_specifier_prerelease(version_info: VersionInfo, spec_
 
 def test_satisfies_path_not_abs_basename_match() -> None:
     info = copy.deepcopy(CURRENT)
-    basename = Path(info.original_executable).stem
+    # stem drops everything from the first dot, so python3.15t arrives as python3 and stops naming a free-threaded
+    # build; only the Windows .exe belongs off the end.
+    name = Path(info.original_executable).name
+    basename = name[: -len(".exe")] if name.endswith(".exe") else name
     spec = PythonSpec.from_string_spec(basename)
     assert info.satisfies(spec, impl_must_match=False) is True
 
diff --git a/tox.toml b/tox.toml
index 20f6da5..c90e125 100644
--- a/tox.toml
+++ b/tox.toml
@@ -1,5 +1,5 @@
 requires = ["tox>=4.38", "tox-uv>=1.29"]
-env_list = ["fix", "3.14", "3.13", "3.12", "3.11", "3.10", "3.9", "3.8", "type-3.8", "type-3.14", "docs", "pkg_meta"]
+env_list = ["fix", "3.15", "3.15t", "3.14", "3.13", "3.12", "3.11", "3.10", "3.9", "3.8", "type-3.8", "type-3.14", "docs", "pkg_meta"]
 skip_missing_interpreters = true
 
 [env_run_base]