diff --git a/.github/workflows/root-ci.yml b/.github/workflows/root-ci.yml
index cf125674dae16..62f1d11953631 100644
--- a/.github/workflows/root-ci.yml
+++ b/.github/workflows/root-ci.yml
@@ -415,10 +415,11 @@ jobs:
             is_special: true
             property: "clang Ninja builtins auto-registration off"
             overrides: ["CMAKE_CXX_STANDARD=20"]
-          # Fedora Rawhide with Python debug build
+          # Fedora Rawhide with Python freethreading+debug build
           - image: rawhide
+            python_venv: "/py-venv-3.14td/ROOT-CI"
             is_special: true
-            property: "Fedora pydebug"
+            property: "Fedora pydebug no GIL"
             overrides: ["CMAKE_CXX_STANDARD=23"]
           # Minimal build
           - image: alma10
@@ -466,14 +467,15 @@ jobs:
       BUILD_DIR: /github/home/ROOT-CI/build
       INSTALL_DIR: /github/home/ROOT-CI/install
       POST_INSTALL_DIR: /github/home/ROOT-CI/PostInstall
+      PYTHON_VENV: ${{ matrix.python_venv || '/py-venv/ROOT-CI' }}
 
     steps:
       - name: Set up environment
         run: |
           ccache -o max_size=${{ matrix.is_special && '5G' || '1.5G' }}
           ccache -s || true
-          if [ -d /py-venv/ROOT-CI/bin/ ]; then
-            . /py-venv/ROOT-CI/bin/activate && echo PATH=$PATH >> $GITHUB_ENV;
+          if [ -d "$PYTHON_VENV/bin/" ]; then
+            . "$PYTHON_VENV/bin/activate" && echo PATH=$PATH >> $GITHUB_ENV;
           fi
           if ${{ contains(matrix.property, 'auto-registration off') }}; then
             echo "Disabling ROOT's object auto registration for this job"
diff --git a/bindings/pyroot/pythonizations/CMakeLists.txt b/bindings/pyroot/pythonizations/CMakeLists.txt
index 2cd037d234b6c..32d7d54b8dad4 100644
--- a/bindings/pyroot/pythonizations/CMakeLists.txt
+++ b/bindings/pyroot/pythonizations/CMakeLists.txt
@@ -37,7 +37,8 @@ if (Python3_VERSION VERSION_GREATER_EQUAL "3.11")
   # On Windows we can't use the stable ABI yet: it requires linking against a
   # different libpython, so as long as we don't build all translation units in
   # the ROOT Pythonization library with the stable ABI we should not use it.
-  if(NOT MSVC)
+  # Free-threaded (Py_GIL_DISABLED) interpreters don't support the limited API.
+  if(NOT MSVC AND NOT Python3_GIL_DISABLED)
     target_compile_options(${libname} PRIVATE -DPy_LIMITED_API=0x030B0000)
   endif()
 endif()
diff --git a/bindings/tpython/CMakeLists.txt b/bindings/tpython/CMakeLists.txt
index c48b3250ffba8..b724647ab0dbc 100644
--- a/bindings/tpython/CMakeLists.txt
+++ b/bindings/tpython/CMakeLists.txt
@@ -36,7 +36,8 @@ if (Python3_VERSION VERSION_GREATER_EQUAL "3.10")
   # On Windows we can't use the stable ABI yet: it requires linking against a
   # different libpython, so as long as we don't build all translation units in
   # the ROOT Pythonization library with the stable ABI we should not use it.
-  if(NOT MSVC)
+  # Free-threaded (Py_GIL_DISABLED) interpreters don't support the limited API.
+  if(NOT MSVC AND NOT Python3_GIL_DISABLED)
     target_compile_options(ROOTTPython PRIVATE -DPy_LIMITED_API=0x030A0000)
   endif()
 endif()
diff --git a/cmake/modules/SearchInstalledSoftware.cmake b/cmake/modules/SearchInstalledSoftware.cmake
index d5727658c9550..09225aa7dbd0b 100644
--- a/cmake/modules/SearchInstalledSoftware.cmake
+++ b/cmake/modules/SearchInstalledSoftware.cmake
@@ -418,6 +418,33 @@ if(tmva-pymva OR tmva-sofie)
 endif()
 find_package(Python3 3.10 COMPONENTS ${python_components})
 
+# Detect whether the found Python interpreter is a free-threaded build
+# (Py_GIL_DISABLED is defined in pyconfig.h). The limited C API is not
+# supported in free-threaded builds; including Python.h with Py_LIMITED_API
+# defined produces a hard error there
+# (https://docs.python.org/3/howto/free-threading-extensions.html).
+# Checking the preprocessor symbol directly is more reliable than asking the
+# interpreter (e.g. sysconfig.get_config_var may misreport, and
+# sys._is_gil_enabled() can be overridden at runtime via PYTHON_GIL=1).
+set(Python3_GIL_DISABLED FALSE)
+if(Python3_Development_FOUND OR Python3_Development.Module_FOUND)
+  include(CheckCXXSourceCompiles)
+  set(_old_required_includes ${CMAKE_REQUIRED_INCLUDES})
+  set(CMAKE_REQUIRED_INCLUDES ${Python3_INCLUDE_DIRS})
+  check_cxx_source_compiles("
+    #include <Python.h>
+    #ifndef Py_GIL_DISABLED
+    #error \"GIL is not disabled\"
+    #endif
+    int main() { return 0; }
+  " ROOT_PYTHON_GIL_DISABLED)
+  set(CMAKE_REQUIRED_INCLUDES ${_old_required_includes})
+  if(ROOT_PYTHON_GIL_DISABLED)
+    set(Python3_GIL_DISABLED TRUE)
+    message(STATUS "Python ${Python3_VERSION} is a free-threaded build (Py_GIL_DISABLED defined); the limited C API will not be used")
+  endif()
+endif()
+
 #---Check for OpenGL installation-------------------------------------------------------
 # OpenGL is required by various graf3d features that are enabled with opengl=ON,
 # or by the Cocoa-related code that always requires it.
diff --git a/roottest/scripts/custom_diff.py b/roottest/scripts/custom_diff.py
index 112c10228ffb6..c16788fb79389 100755
--- a/roottest/scripts/custom_diff.py
+++ b/roottest/scripts/custom_diff.py
@@ -33,6 +33,7 @@ def __init__(self):
                 r"^In file included from input_line",  # Wrapper input line
                 r"^[:space:]*$",  # Lines which are empty apart from spaces
                 r"^Info in <TROOT>: Object auto registration",  # ROOT 7 mode
+                r"^<frozen importlib\._bootstrap>:\d+: RuntimeWarning: The global interpreter lock \(GIL\) has been enabled",  # Free-threaded Python re-enabling the GIL to load a C extension that isn't GIL-safe
             ]
         ]