diff --git a/.pre-commit-config.yaml b/.pre-commit-config.yaml
index b1e1e1e1..2f101744 100644
--- a/.pre-commit-config.yaml
+++ b/.pre-commit-config.yaml
@@ -34,10 +34,6 @@ repos:
     hooks:
       - id: ruff
         args: [--fix, --exit-non-zero-on-fix]
-  - repo: https://github.com/PyCQA/isort
-    rev: 5.13.2
-    hooks:
-      - id: isort
   - repo: https://github.com/psf/black
     rev: 24.10.0
     hooks:
diff --git a/Makefile b/Makefile
index 054d1e8c..2bb23346 100644
--- a/Makefile
+++ b/Makefile
@@ -66,8 +66,8 @@ flake8-install:
 
 .PHONY: py-format-install
 py-format-install:
-	$(call check_pip_install,isort)
 	$(call check_pip_install,black)
+	$(call check_pip_install,ruff)
 
 .PHONY: ruff-install
 ruff-install:
@@ -156,10 +156,10 @@ flake8: flake8-install
 
 .PHONY: py-format
 py-format: py-format-install
-	$(PYTHON) -m isort --version
 	$(PYTHON) -m black --version
-	$(PYTHON) -m isort --project $(PROJECT_PATH) --check $(PYTHON_FILES) && \
-	$(PYTHON) -m black --check $(PYTHON_FILES)
+	$(PYTHON) -m ruff --version
+	$(PYTHON) -m black --check $(PYTHON_FILES) && \
+	$(PYTHON) -m ruff check --select=I $(PYTHON_FILES)
 
 .PHONY: ruff
 ruff: ruff-install
@@ -252,7 +252,6 @@ lint: ruff flake8 py-format mypy pylint doctest clang-format clang-tidy cpplint
 
 .PHONY: format
 format: py-format-install ruff-install clang-format-install addlicense-install
-	$(PYTHON) -m isort --project $(PROJECT_PATH) $(PYTHON_FILES)
 	$(PYTHON) -m black $(PYTHON_FILES)
 	$(PYTHON) -m ruff check --fix --exit-zero .
 	$(CLANG_FORMAT) -style=file -i $(CXX_FILES)
diff --git a/conda-recipe.yaml b/conda-recipe.yaml
index f3d199dd..eca143aa 100644
--- a/conda-recipe.yaml
+++ b/conda-recipe.yaml
@@ -65,7 +65,6 @@ dependencies:
   - conda-forge::pytest
   - conda-forge::pytest-cov
   - conda-forge::pytest-xdist
-  - conda-forge::isort
   - conda-forge::black
   - conda-forge::pylint
   - conda-forge::mypy
diff --git a/optree/functools.py b/optree/functools.py
index e3351f4d..4a056685 100644
--- a/optree/functools.py
+++ b/optree/functools.py
@@ -18,8 +18,10 @@
 
 import functools
 from typing import TYPE_CHECKING, Any, Callable, ClassVar
-from typing_extensions import Self  # Python 3.11+
-from typing_extensions import deprecated  # Python 3.13+
+from typing_extensions import (
+    Self,  # Python 3.11+
+    deprecated,  # Python 3.13+
+)
 
 from optree import registry
 from optree.accessor import GetAttrEntry
diff --git a/optree/registry.py b/optree/registry.py
index e2a2978b..a445d48b 100644
--- a/optree/registry.py
+++ b/optree/registry.py
@@ -40,8 +40,10 @@
     TypeVar,
     overload,
 )
-from typing_extensions import TypeAlias  # Python 3.10+
-from typing_extensions import deprecated  # Python 3.13+
+from typing_extensions import (
+    TypeAlias,  # Python 3.10+
+    deprecated,  # Python 3.13+
+)
 
 from optree import _C
 from optree.accessor import (
diff --git a/optree/typing.py b/optree/typing.py
index 192052fb..939df3bc 100644
--- a/optree/typing.py
+++ b/optree/typing.py
@@ -47,10 +47,12 @@
     ValuesView,
     runtime_checkable,
 )
-from typing_extensions import NamedTuple  # Generic NamedTuple: Python 3.11+
-from typing_extensions import ParamSpec  # Python 3.10+
-from typing_extensions import Self  # Python 3.11+
-from typing_extensions import TypeAlias  # Python 3.10+
+from typing_extensions import (
+    NamedTuple,  # Generic NamedTuple: Python 3.11+
+    ParamSpec,  # Python 3.10+
+    Self,  # Python 3.11+
+    TypeAlias,  # Python 3.10+
+)
 
 from optree import _C
 from optree._C import PyTreeKind, PyTreeSpec
diff --git a/pyproject.toml b/pyproject.toml
index 5cd86cca..8075bac7 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -56,7 +56,6 @@ jax = ["jax"]
 numpy = ["numpy"]
 torch = ["torch"]
 lint = [
-    "isort",
     "black",
     "pylint[spelling]",
     "mypy",
@@ -124,16 +123,6 @@ line-length = 100
 skip-string-normalization = true
 target-version = ["py38"]
 
-[tool.isort]
-atomic = true
-profile = "black"
-src_paths = ["optree", "tests"]
-extra_standard_library = ["typing_extensions"]
-indent = 4
-line_length = 100
-lines_after_imports = 2
-multi_line_output = 3
-
 [tool.mypy]
 python_version = "3.8"
 exclude = ["^setup\\.py$", "^tests/.*\\.py$"]
@@ -186,6 +175,7 @@ src = ["optree", "tests"]
 select = [
     "E", "W",  # pycodestyle
     "F",       # pyflakes
+    "I",       # isort
     "C90",     # mccabe
     "N",       # pep8-naming
     "UP",      # pyupgrade
@@ -272,6 +262,12 @@ typing-modules = ["optree.typing"]
     "ANN",     # flake8-annotations
 ]
 
+[tool.ruff.lint.isort]
+known-first-party = ["optree"]
+known-local-folder = ["optree", "tests"]
+extra-standard-library = ["typing_extensions"]
+lines-after-imports = 2
+
 [tool.ruff.lint.pydocstyle]
 convention = "google"
 
diff --git a/tests/requirements.txt b/tests/requirements.txt
index 8d8def5d..857e6777 100644
--- a/tests/requirements.txt
+++ b/tests/requirements.txt
@@ -3,7 +3,6 @@
 pytest
 pytest-cov
 pytest-xdist
-isort
 black
 pylint[spelling]
 mypy