diff --git a/newsfragments/33.feature.rst b/newsfragments/33.feature.rst
new file mode 100644
index 0000000..508e13b
--- /dev/null
+++ b/newsfragments/33.feature.rst
@@ -0,0 +1 @@
+Moved the metadata into ``PEP 621``-compliant ``pyproject.toml``.
diff --git a/pyproject.toml b/pyproject.toml
index ecd1160..64cf62a 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -1,7 +1,44 @@
 [build-system]
-requires = ["setuptools>=42.2", "setuptools_scm[toml]>=3.4.3"]
+requires = ["setuptools>=61.2", "setuptools_scm[toml]>=3.4.3"]
 build-backend = "setuptools.build_meta"
 
+[project]
+name = "sniffio"
+authors = [{name = "Nathaniel J. Smith", email = "njs@pobox.com"}]
+license = {text = "MIT OR Apache-2.0"}
+description = "Sniff out which async library your code is running under"
+readme = "README.rst"
+keywords = ["async", "trio", "asyncio"]
+classifiers = [
+    "License :: OSI Approved :: MIT License",
+    "License :: OSI Approved :: Apache Software License",
+    "Framework :: Trio",
+    "Framework :: AsyncIO",
+    "Operating System :: POSIX :: Linux",
+    "Operating System :: MacOS :: MacOS X",
+    "Operating System :: Microsoft :: Windows",
+    "Programming Language :: Python :: 3 :: Only",
+    "Programming Language :: Python :: Implementation :: CPython",
+    "Programming Language :: Python :: Implementation :: PyPy",
+    "Intended Audience :: Developers",
+    "Development Status :: 5 - Production/Stable",
+]
+urls = {Homepage = "https://github.com/python-trio/sniffio"}
+requires-python = ">=3.7"
+dynamic = ["version"]
+
+[project.optional-dependencies]
+testing = ["curio"]
+
+[tool.setuptools]
+include-package-data = false
+
+[tool.setuptools.packages]
+find = {namespaces = false}
+
+[tool.setuptools.package-data]
+sniffio = ["py.typed"]
+
 [tool.setuptools_scm]
 write_to = "sniffio/_version.py"
 write_to_template = "__version__ = \"{version}\"\n"
diff --git a/setup.cfg b/setup.cfg
deleted file mode 100644
index 757d144..0000000
--- a/setup.cfg
+++ /dev/null
@@ -1,30 +0,0 @@
-[metadata]
-name = sniffio
-author = Nathaniel J. Smith
-author_email = njs@pobox.com
-license = MIT OR Apache-2.0
-description = Sniff out which async library your code is running under
-long_description = file: README.rst
-keywords = async, trio, asyncio
-url = https://github.com/python-trio/sniffio
-classifiers =
-    License :: OSI Approved :: MIT License
-    License :: OSI Approved :: Apache Software License
-    Framework :: Trio
-    Framework :: AsyncIO
-    Operating System :: POSIX :: Linux
-    Operating System :: MacOS :: MacOS X
-    Operating System :: Microsoft :: Windows
-    Programming Language :: Python :: 3 :: Only
-    Programming Language :: Python :: Implementation :: CPython
-    Programming Language :: Python :: Implementation :: PyPy
-    Intended Audience :: Developers
-    Development Status :: 5 - Production/Stable
-
-[options]
-packages = find:
-python_requires = >=3.7
-tests_require = curio
-
-[options.package_data]
-sniffio = py.typed