diff --git a/.github/copilot-instructions.md b/.github/copilot-instructions.md
index 96f1e35..80378d2 100644
--- a/.github/copilot-instructions.md
+++ b/.github/copilot-instructions.md
@@ -6,7 +6,7 @@
 
 ### Technology Stack
 
-- **Python**: 3.9+
+- **Python**: 3.10+
 - **Core**: NumPy (≥1.21), QtPy (≥1.9)
 - **GUI**: Qt via QtPy (PyQt5/PyQt6/PySide6)
 - **Testing**: pytest
diff --git a/.github/workflows/test-PyQt5.yml b/.github/workflows/test-PyQt5.yml
index 07fac8c..7ff71c6 100644
--- a/.github/workflows/test-PyQt5.yml
+++ b/.github/workflows/test-PyQt5.yml
@@ -22,7 +22,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        python-version: ["3.9", "3.11", "3.13", "3.14"]
+        python-version: ["3.10", "3.11", "3.13", "3.14"]
 
     steps:
     - uses: actions/checkout@v7
diff --git a/.github/workflows/test-PyQt6.yml b/.github/workflows/test-PyQt6.yml
index 0209ac9..2af2b1c 100644
--- a/.github/workflows/test-PyQt6.yml
+++ b/.github/workflows/test-PyQt6.yml
@@ -22,7 +22,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        python-version: ["3.9", "3.11", "3.13", "3.14"]
+        python-version: ["3.10", "3.11", "3.13", "3.14"]
 
     steps:
     - uses: actions/checkout@v7
diff --git a/.github/workflows/test-PySide6.yml b/.github/workflows/test-PySide6.yml
index fdc1441..e2cdaec 100644
--- a/.github/workflows/test-PySide6.yml
+++ b/.github/workflows/test-PySide6.yml
@@ -22,7 +22,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        python-version: ["3.9", "3.11", "3.13", "3.14"]
+        python-version: ["3.10", "3.11", "3.13", "3.14"]
 
     steps:
     - uses: actions/checkout@v7
diff --git a/CHANGELOG.md b/CHANGELOG.md
index ada1e22..23ce154 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,5 +1,11 @@
 # PythonQwt Releases
 
+## Unreleased
+
+### Requirements
+
+- Python 3.10 or later is now required. Python 3.9 users must keep an earlier compatible release.
+
 ## Version 0.16.3
 
 ### New features
diff --git a/README.md b/README.md
index 0c3db65..a4263f6 100644
--- a/README.md
+++ b/README.md
@@ -100,7 +100,7 @@ Compatibility table:
 
 ### Requirements
 
-- Python >=3.9
+- Python >=3.10
 - QtPy >= 1.9 (and a Python-to-Qt binding library, see above)
 - NumPy >= 1.21
 
diff --git a/doc/installation.rst b/doc/installation.rst
index 7b840f2..dcefee8 100644
--- a/doc/installation.rst
+++ b/doc/installation.rst
@@ -5,7 +5,7 @@ Dependencies
 ------------
 
 Requirements:
-    * Python 3.9 or higher
+    * Python 3.10 or higher
     * PyQt5 5.15, PyQt6 or PySide6
     * QtPy 1.9 or higher
     * NumPy 1.21 or higher
diff --git a/pyproject.toml b/pyproject.toml
index 581f481..9b9680b 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -23,14 +23,13 @@ classifiers = [
     "Operating System :: OS Independent",
     "Operating System :: POSIX",
     "Operating System :: Unix",
-    "Programming Language :: Python :: 3.9",
     "Programming Language :: Python :: 3.10",
     "Programming Language :: Python :: 3.11",
     "Programming Language :: Python :: 3.12",
     "Programming Language :: Python :: 3.13",
     "Programming Language :: Python :: 3.14",
 ]
-requires-python = ">=3.9, <4"
+requires-python = ">=3.10, <4"
 dependencies = ["NumPy>=1.21", "QtPy>=1.9"]
 dynamic = ["version"]
 
@@ -62,7 +61,7 @@ addopts = "qwt"
 exclude = [".git", ".vscode", "build", "dist","venv*",".venv*"]
 line-length = 88                               # Same as Black.
 indent-width = 4                               # Same as Black.
-target-version = "py39"                        # Assume Python 3.9.
+target-version = "py310"                       # Assume Python 3.10.
 
 [tool.ruff.lint]
 # all rules can be found here: https://beta.ruff.rs/docs/rules/