diff --git a/cmake/modules/FindEigen3.cmake b/cmake/modules/FindEigen3.cmake
index e33a2678..a85bd43a 100644
--- a/cmake/modules/FindEigen3.cmake
+++ b/cmake/modules/FindEigen3.cmake
@@ -114,7 +114,17 @@ else ()
   # the script will work as usual
   # re:NO_CMAKE_PACKAGE_REGISTRY: eigen3 registers its *build* tree with the user package registry ...
   #                               to avoid issues with wiped build directory look for installed eigen
-  find_package(Eigen3 ${Eigen3_FIND_VERSION} NO_MODULE QUIET NO_CMAKE_PACKAGE_REGISTRY)
+  # N.B. Eigen3.4 -> Eigen5 transition made versions reported in Eigen3Config useless, will check manually below
+  find_package(Eigen3 NO_MODULE QUIET NO_CMAKE_PACKAGE_REGISTRY)
+
+  # if found older version, reset and try to look for include path directly
+  if (EIGEN3_INCLUDE_DIR)
+    _eigen3_check_version()
+    if (NOT EIGEN3_VERSION_OK)
+      unset(Eigen3_CONFIG)
+      unset(EIGEN3_INCLUDE_DIR)
+    endif()
+  endif()
 
   if(NOT EIGEN3_INCLUDE_DIR)
     find_path(EIGEN3_INCLUDE_DIR NAMES signature_of_eigen3_matrix_library
diff --git a/export/CMakeLists.txt.export b/export/CMakeLists.txt.export
index 45fb1a78..62f3f262 100644
--- a/export/CMakeLists.txt.export
+++ b/export/CMakeLists.txt.export
@@ -169,8 +169,14 @@ endif()
 
 find_package(Eigen3 MODULE)
 
+set(LIBINT2_CXX_STANDARD 11)
 if (TARGET Eigen3::Eigen)
     set(LIBINT_HAS_EIGEN 1)
+    # Eigen 3.5+ (a.k.a. Eigen 5) requires C++14
+    if (EIGEN3_VERSION VERSION_GREATER_EQUAL "3.5.0")
+        set(LIBINT2_CXX_STANDARD 14)
+        message(STATUS "Eigen ${EIGEN3_VERSION} requires C++14; setting LIBINT2_CXX_STANDARD=14")
+    endif()
 endif()
 if (LIBINT2_REQUIRE_CXX_API AND NOT LIBINT_HAS_EIGEN)
     message(FATAL_ERROR "C++ API cannot be built without Eigen3; configure (via CMake) and install Eigen3 and add the install prefix to CMAKE_PREFIX_PATH, or add -D LIBINT2_REQUIRE_CXX_API=OFF to the CMake command line if the C++ API is not required")
@@ -231,7 +237,7 @@ add_library(
 target_compile_features(
   int-obj
   PUBLIC
-    "cxx_std_11"  # N.B. PUBLIC to make int-{static/shared} require C++11
+    "cxx_std_${LIBINT2_CXX_STANDARD}"  # N.B. PUBLIC to make int-{static/shared} require C++11 (or C++14 for Eigen 5.x)
   )
 target_compile_definitions(
   int-obj
@@ -268,7 +274,7 @@ if (LIBINT2_REQUIRE_CXX_API_COMPILED)
     target_compile_features(
       int-cxx-obj
       PUBLIC
-        "cxx_std_11"
+        "cxx_std_${LIBINT2_CXX_STANDARD}"
       )
     target_compile_definitions(
       int-cxx-obj
@@ -336,7 +342,7 @@ if (L2_BUILD_SHARED_LIBS)
     target_compile_features(
       int-shared
       INTERFACE
-        "cxx_std_11"
+        "cxx_std_${LIBINT2_CXX_STANDARD}"
       )
     target_compile_definitions(
       int-shared
@@ -386,7 +392,7 @@ if (L2_BUILD_SHARED_LIBS)
         target_compile_features(
           int-cxx-headeronly-shared
           INTERFACE
-            "cxx_std_11"
+            "cxx_std_${LIBINT2_CXX_STANDARD}"
           )
         target_compile_definitions(
           int-cxx-headeronly-shared
@@ -467,7 +473,7 @@ if (L2_BUILD_STATIC_LIBS)
     target_compile_features(
       int-static
       INTERFACE
-        "cxx_std_11"
+        "cxx_std_${LIBINT2_CXX_STANDARD}"
       )
     target_compile_definitions(
       int-static
@@ -510,7 +516,7 @@ if (L2_BUILD_STATIC_LIBS)
         target_compile_features(
           int-cxx-headeronly-static
           INTERFACE
-            "cxx_std_11"
+            "cxx_std_${LIBINT2_CXX_STANDARD}"
           )
         target_compile_definitions(
           int-cxx-headeronly-static