diff --git a/MANIFEST.in b/MANIFEST.in
index a5cd439d0..25d6814dc 100644
--- a/MANIFEST.in
+++ b/MANIFEST.in
@@ -8,6 +8,6 @@ prune docs/build
 
 recursive-include examples *.py *.crt *.key *.pem *.csr
 
-include README.rst LICENSE CHANGELOG.rst tox.ini
+include README.rst LICENSE CHANGELOG.rst pyproject.toml
 
 global-exclude *.pyc *.pyo *.swo *.swp *.map *.yml *.DS_Store
diff --git a/pyproject.toml b/pyproject.toml
index bc191a5f9..b3f1904f5 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -49,6 +49,13 @@ classifiers = [
 "Documentation" = "https://python-hyper.org/"
 
 [dependency-groups]
+dev = [
+  { include-group = "testing" },
+  { include-group = "linting" },
+  { include-group = "packaging" },
+  { include-group = "docs" },
+]
+
 testing = [
   "pytest>=8.3.3,<9",
   "pytest-cov>=6.0.0,<7",
@@ -109,3 +116,89 @@ source = [
   "src/",
   ".tox/**/site-packages/",
 ]
+
+[tool.tox]
+min_version = "4.23.2"
+env_list = [ "py39", "py310", "py311", "py312", "py313", "pypy3", "lint", "docs", "packaging" ]
+
+[tool.tox.gh-actions]
+python = """
+  3.9: py39, h2spec, lint, docs, packaging
+  3.10: py310
+  3.11: py311
+  3.12: py312
+  3.13: py313
+  pypy3: pypy3
+"""
+
+[tool.tox.env_run_base]
+pass_env = [
+  "GITHUB_*",
+]
+dependency_groups = ["testing"]
+commands = [
+  ["python", "-bb", "-m", "pytest", "--cov-report=xml", "--cov-report=term", "--cov=h2", { replace = "posargs", extend = true }]
+]
+
+[tool.tox.env.pypy3]
+# temporarily disable coverage testing on PyPy due to performance problems
+commands = [
+  ["pytest", { replace = "posargs", extend = true }]
+]
+
+[tool.tox.env.lint]
+dependency_groups = ["linting"]
+commands = [
+  ["ruff", "check", "src/"],
+  # TODO: ["mypy", "src/"],
+]
+
+[tool.tox.env.docs]
+dependency_groups = ["docs"]
+allowlist_externals = ["make"]
+changedir = "{toxinidir}/docs"
+commands = [
+  ["make", "clean"],
+  ["make", "html"],
+]
+
+[tool.tox.env.packaging]
+base_python = ["python39"]
+dependency_groups = ["packaging"]
+allowlist_externals = ["rm"]
+commands = [
+  ["rm", "-rf", "dist/"],
+  ["check-manifest"],
+  ["python", "-m", "build", "--outdir", "dist/"],
+  ["twine", "check", "dist/*"],
+]
+
+[tool.tox.env.publish]
+base_python = "{[tool.tox.env.packaging]base_python}"
+deps = "{[tool.tox.env.packaging]deps}"
+allowlist_externals = "{[tool.tox.env.packaging]allowlist_externals}"
+commands = [
+    "{[testenv:packaging]commands}",
+    ["twine", "upload", "dist/*"],
+]
+
+[tool.tox.env.graphs]
+basepython = ["python3.9"]
+deps = [
+  "graphviz==0.14.1",
+]
+commands = [
+    ["python", "visualizer/visualize.py", "-i", "docs/source/_static"],
+]
+
+[tool.tox.env.h2spec]
+basepython = ["python3.9"]
+deps = [
+  "twisted[tls]==20.3.0",
+]
+allowlist_externals = [
+  "{toxinidir}/tests/h2spectest.sh"
+]
+commands = [
+  ["{toxinidir}/tests/h2spectest.sh"],
+]
diff --git a/tox.ini b/tox.ini
deleted file mode 100644
index 930d3bff6..000000000
--- a/tox.ini
+++ /dev/null
@@ -1,71 +0,0 @@
-[tox]
-envlist = py39, py310, py311, py312, py313, pypy3, lint, docs, packaging
-
-[gh-actions]
-python =
-    3.9: py39, lint, docs, packaging, h2spec
-    3.10: py310
-    3.11: py311
-    3.12: py312
-    3.13: py313
-    pypy3: pypy3
-
-[testenv]
-passenv =
-    GITHUB_*
-dependency_groups = testing
-commands =
-    python -bb -m pytest --cov-report=xml  --cov-report=term --cov=h2 {posargs}
-
-[testenv:pypy3]
-# temporarily disable coverage testing on PyPy due to performance problems
-commands = pytest {posargs}
-
-[testenv:lint]
-dependency_groups = linting
-allowlist_externals =
-    ruff
-commands =
-    ruff check src/ tests/
-
-[testenv:docs]
-dependency_groups = docs
-allowlist_externals = make
-changedir = {toxinidir}/docs
-commands =
-    make clean
-    make html
-
-[testenv:packaging]
-basepython = python3.9
-dependency_groups = packaging
-allowlist_externals = rm
-commands =
-    rm -rf dist/
-    check-manifest
-    python -m build --outdir dist/
-    twine check dist/*
-
-[testenv:publish]
-basepython = {[testenv:packaging]basepython}
-deps =
-    {[testenv:packaging]deps}
-allowlist_externals = {[testenv:packaging]allowlist_externals}
-commands =
-    {[testenv:packaging]commands}
-    twine upload dist/*
-
-[testenv:graphs]
-basepython = python3.9
-deps =
-    graphviz==0.14.1
-commands =
-    python visualizer/visualize.py -i docs/source/_static
-
-[testenv:h2spec]
-basepython = python3.9
-deps =
-    twisted[tls]==20.3.0
-allowlist_externals = {toxinidir}/test/h2spectest.sh
-commands =
-    {toxinidir}/test/h2spectest.sh