diff --git a/src/CMakeLists.txt b/src/CMakeLists.txt
index b52122fc..5c724a46 100644
--- a/src/CMakeLists.txt
+++ b/src/CMakeLists.txt
@@ -116,6 +116,7 @@ set(INTERNAL_HEADERS
     ${SOURCES_DIR}/internal/catch_platform.hpp
     ${SOURCES_DIR}/internal/catch_polyfills.hpp
     ${SOURCES_DIR}/internal/catch_preprocessor.hpp
+    ${SOURCES_DIR}/internal/catch_preprocessor_remove_parens.hpp
     ${SOURCES_DIR}/internal/catch_random_number_generator.hpp
     ${SOURCES_DIR}/internal/catch_random_seed_generation.hpp
     ${SOURCES_DIR}/reporters/catch_reporter_registrars.hpp
diff --git a/src/catch2/benchmark/detail/catch_stats.cpp b/src/catch2/benchmark/detail/catch_stats.cpp
index deba9a0e..8f13f59a 100644
--- a/src/catch2/benchmark/detail/catch_stats.cpp
+++ b/src/catch2/benchmark/detail/catch_stats.cpp
@@ -13,6 +13,7 @@
 #include <catch2/internal/catch_compiler_detections.hpp>
 
 #include <cassert>
+#include <cstddef>
 #include <iterator>
 #include <random>
 
diff --git a/src/catch2/catch_all.hpp b/src/catch2/catch_all.hpp
index 77dd00c3..79f38f3b 100644
--- a/src/catch2/catch_all.hpp
+++ b/src/catch2/catch_all.hpp
@@ -80,6 +80,7 @@
 #include <catch2/internal/catch_platform.hpp>
 #include <catch2/internal/catch_polyfills.hpp>
 #include <catch2/internal/catch_preprocessor.hpp>
+#include <catch2/internal/catch_preprocessor_remove_parens.hpp>
 #include <catch2/internal/catch_random_number_generator.hpp>
 #include <catch2/internal/catch_random_seed_generation.hpp>
 #include <catch2/internal/catch_reporter_registry.hpp>
diff --git a/src/catch2/catch_approx.cpp b/src/catch2/catch_approx.cpp
index 50cb75c3..21652111 100644
--- a/src/catch2/catch_approx.cpp
+++ b/src/catch2/catch_approx.cpp
@@ -7,6 +7,7 @@
 // SPDX-License-Identifier: BSL-1.0
 #include <catch2/catch_approx.hpp>
 #include <catch2/internal/catch_enforce.hpp>
+#include <catch2/internal/catch_stream.hpp>
 
 #include <cmath>
 #include <limits>
diff --git a/src/catch2/catch_config.cpp b/src/catch2/catch_config.cpp
index b96cf46a..1f631f45 100644
--- a/src/catch2/catch_config.cpp
+++ b/src/catch2/catch_config.cpp
@@ -16,8 +16,6 @@
 #include <catch2/internal/catch_test_spec_parser.hpp>
 #include <catch2/interfaces/catch_interfaces_tag_alias_registry.hpp>
 
-#include <ostream>
-
 namespace Catch {
 
     bool operator==( ProcessedReporterSpec const& lhs,
diff --git a/src/catch2/catch_config.hpp b/src/catch2/catch_config.hpp
index 2b57bbb5..8823accd 100644
--- a/src/catch2/catch_config.hpp
+++ b/src/catch2/catch_config.hpp
@@ -9,16 +9,17 @@
 #define CATCH_CONFIG_HPP_INCLUDED
 
 #include <catch2/catch_test_spec.hpp>
-#include <catch2/catch_user_config.hpp>
 #include <catch2/interfaces/catch_interfaces_config.hpp>
 #include <catch2/internal/catch_unique_ptr.hpp>
 #include <catch2/internal/catch_optional.hpp>
+#include <catch2/internal/catch_stringref.hpp>
 #include <catch2/internal/catch_random_seed_generation.hpp>
 #include <catch2/internal/catch_reporter_spec_parser.hpp>
 
-#include <iosfwd>
-#include <vector>
+#include <chrono>
+#include <map>
 #include <string>
+#include <vector>
 
 namespace Catch {
 
diff --git a/src/catch2/catch_test_case_info.cpp b/src/catch2/catch_test_case_info.cpp
index 83cfcc8e..6d89dc72 100644
--- a/src/catch2/catch_test_case_info.cpp
+++ b/src/catch2/catch_test_case_info.cpp
@@ -7,8 +7,6 @@
 // SPDX-License-Identifier: BSL-1.0
 #include <catch2/catch_test_case_info.hpp>
 #include <catch2/internal/catch_enforce.hpp>
-#include <catch2/catch_test_spec.hpp>
-#include <catch2/interfaces/catch_interfaces_testcase.hpp>
 #include <catch2/internal/catch_string_manip.hpp>
 #include <catch2/internal/catch_case_insensitive_comparisons.hpp>
 
diff --git a/src/catch2/catch_test_macros.hpp b/src/catch2/catch_test_macros.hpp
index dde1c9cd..e92a45f0 100644
--- a/src/catch2/catch_test_macros.hpp
+++ b/src/catch2/catch_test_macros.hpp
@@ -11,7 +11,6 @@
 #include <catch2/internal/catch_test_macro_impl.hpp>
 #include <catch2/catch_message.hpp>
 #include <catch2/catch_user_config.hpp>
-#include <catch2/internal/catch_preprocessor.hpp>
 #include <catch2/internal/catch_section.hpp>
 #include <catch2/internal/catch_test_registry.hpp>
 #include <catch2/internal/catch_unique_name.hpp>
diff --git a/src/catch2/catch_totals.hpp b/src/catch2/catch_totals.hpp
index 7ab6a1b6..6bc444fc 100644
--- a/src/catch2/catch_totals.hpp
+++ b/src/catch2/catch_totals.hpp
@@ -8,7 +8,6 @@
 #ifndef CATCH_TOTALS_HPP_INCLUDED
 #define CATCH_TOTALS_HPP_INCLUDED
 
-#include <cstddef>
 #include <cstdint>
 
 namespace Catch {
diff --git a/src/catch2/generators/catch_generators.hpp b/src/catch2/generators/catch_generators.hpp
index 948d6f0f..acfdb7dc 100644
--- a/src/catch2/generators/catch_generators.hpp
+++ b/src/catch2/generators/catch_generators.hpp
@@ -12,6 +12,8 @@
 #include <catch2/internal/catch_source_line_info.hpp>
 #include <catch2/internal/catch_stringref.hpp>
 #include <catch2/internal/catch_move_and_forward.hpp>
+#include <catch2/internal/catch_unique_name.hpp>
+#include <catch2/internal/catch_preprocessor.hpp>
 
 #include <vector>
 #include <tuple>
diff --git a/src/catch2/internal/catch_assertion_handler.hpp b/src/catch2/internal/catch_assertion_handler.hpp
index 4d397766..5faa5e4b 100644
--- a/src/catch2/internal/catch_assertion_handler.hpp
+++ b/src/catch2/internal/catch_assertion_handler.hpp
@@ -13,11 +13,11 @@
 #include <catch2/interfaces/catch_interfaces_capture.hpp>
 #include <catch2/internal/catch_lazy_expr.hpp>
 
+#include <string>
+
 namespace Catch {
 
-    struct AssertionResultData;
     class IResultCapture;
-    class RunContext;
 
     struct AssertionReaction {
         bool shouldDebugBreak = false;
diff --git a/src/catch2/internal/catch_case_insensitive_comparisons.hpp b/src/catch2/internal/catch_case_insensitive_comparisons.hpp
index 5742e6b7..c182e13e 100644
--- a/src/catch2/internal/catch_case_insensitive_comparisons.hpp
+++ b/src/catch2/internal/catch_case_insensitive_comparisons.hpp
@@ -10,8 +10,6 @@
 
 #include <catch2/internal/catch_stringref.hpp>
 
-#include <string>
-
 namespace Catch {
     namespace Detail {
         //! Provides case-insensitive `op<` semantics when called
diff --git a/src/catch2/internal/catch_clara.cpp b/src/catch2/internal/catch_clara.cpp
index df844838..a4701a81 100644
--- a/src/catch2/internal/catch_clara.cpp
+++ b/src/catch2/internal/catch_clara.cpp
@@ -5,13 +5,16 @@
 //        https://www.boost.org/LICENSE_1_0.txt)
 
 // SPDX-License-Identifier: BSL-1.0
-#include <algorithm>
+
 #include <catch2/internal/catch_clara.hpp>
 #include <catch2/internal/catch_console_width.hpp>
 #include <catch2/internal/catch_platform.hpp>
 #include <catch2/internal/catch_string_manip.hpp>
 #include <catch2/internal/catch_textflow.hpp>
 
+#include <algorithm>
+#include <ostream>
+
 namespace {
     bool isOptPrefix( char c ) {
         return c == '-'
diff --git a/src/catch2/internal/catch_clara.hpp b/src/catch2/internal/catch_clara.hpp
index add00c0d..6e3138ae 100644
--- a/src/catch2/internal/catch_clara.hpp
+++ b/src/catch2/internal/catch_clara.hpp
@@ -35,7 +35,6 @@
 #include <catch2/internal/catch_void_type.hpp>
 
 #include <cassert>
-#include <cctype>
 #include <memory>
 #include <ostream>
 #include <sstream>
diff --git a/src/catch2/internal/catch_commandline.cpp b/src/catch2/internal/catch_commandline.cpp
index fb2275d1..81787aa9 100644
--- a/src/catch2/internal/catch_commandline.cpp
+++ b/src/catch2/internal/catch_commandline.cpp
@@ -13,11 +13,9 @@
 #include <catch2/internal/catch_string_manip.hpp>
 #include <catch2/interfaces/catch_interfaces_registry_hub.hpp>
 #include <catch2/interfaces/catch_interfaces_reporter_registry.hpp>
-#include <catch2/interfaces/catch_interfaces_reporter.hpp>
 #include <catch2/internal/catch_console_colour.hpp>
 #include <catch2/internal/catch_reporter_spec_parser.hpp>
 
-#include <algorithm>
 #include <fstream>
 #include <string>
 
diff --git a/src/catch2/internal/catch_console_colour.cpp b/src/catch2/internal/catch_console_colour.cpp
index ae22d67b..e2a175f1 100644
--- a/src/catch2/internal/catch_console_colour.cpp
+++ b/src/catch2/internal/catch_console_colour.cpp
@@ -16,6 +16,7 @@
 #include <catch2/internal/catch_errno_guard.hpp>
 #include <catch2/interfaces/catch_interfaces_config.hpp>
 #include <catch2/internal/catch_stream.hpp>
+#include <catch2/internal/catch_move_and_forward.hpp>
 #include <catch2/internal/catch_context.hpp>
 #include <catch2/internal/catch_platform.hpp>
 #include <catch2/internal/catch_debugger.hpp>
@@ -23,7 +24,9 @@
 #include <catch2/internal/catch_compiler_capabilities.hpp>
 #include <catch2/internal/catch_compiler_detections.hpp>
 
+#include <cassert>
 #include <ostream>
+#include <utility>
 
 namespace Catch {
 
diff --git a/src/catch2/internal/catch_console_colour.hpp b/src/catch2/internal/catch_console_colour.hpp
index 661078af..aa3d83a2 100644
--- a/src/catch2/internal/catch_console_colour.hpp
+++ b/src/catch2/internal/catch_console_colour.hpp
@@ -16,7 +16,6 @@
 namespace Catch {
 
     enum class ColourMode : std::uint8_t;
-    class IConfig;
     class IStream;
 
     struct Colour {
diff --git a/src/catch2/internal/catch_debug_console.cpp b/src/catch2/internal/catch_debug_console.cpp
index 5942524e..d13cc0bb 100644
--- a/src/catch2/internal/catch_debug_console.cpp
+++ b/src/catch2/internal/catch_debug_console.cpp
@@ -11,6 +11,8 @@
 #include <catch2/internal/catch_platform.hpp>
 #include <catch2/internal/catch_windows_h_proxy.hpp>
 
+#include <iosfwd>
+
 #if defined(CATCH_CONFIG_ANDROID_LOGWRITE)
 #include <android/log.h>
 
diff --git a/src/catch2/internal/catch_preprocessor.hpp b/src/catch2/internal/catch_preprocessor.hpp
index 3aac18df..f3156316 100644
--- a/src/catch2/internal/catch_preprocessor.hpp
+++ b/src/catch2/internal/catch_preprocessor.hpp
@@ -9,6 +9,7 @@
 #define CATCH_PREPROCESSOR_HPP_INCLUDED
 
 #include <catch2/internal/catch_compiler_detections.hpp>
+#include <catch2/internal/catch_preprocessor_remove_parens.hpp>
 
 #if defined(CATCH_COMPILER_GCC)
 // We need to silence "empty __VA_ARGS__ warning", and using just _Pragma does not work
@@ -60,10 +61,6 @@
 
 #define CATCH_REC_LIST(f, ...) CATCH_RECURSE(CATCH_REC_LIST2(f, __VA_ARGS__, ()()(), ()()(), ()()(), 0))
 
-#define INTERNAL_CATCH_EXPAND1(param) INTERNAL_CATCH_EXPAND2(param)
-#define INTERNAL_CATCH_EXPAND2(...) INTERNAL_CATCH_NO## __VA_ARGS__
-#define INTERNAL_CATCH_DEF(...) INTERNAL_CATCH_DEF __VA_ARGS__
-#define INTERNAL_CATCH_NOINTERNAL_CATCH_DEF
 #define INTERNAL_CATCH_STRINGIZE(...) INTERNAL_CATCH_STRINGIZE2(__VA_ARGS__)
 #ifndef CATCH_CONFIG_TRADITIONAL_MSVC_PREPROCESSOR
 #define INTERNAL_CATCH_STRINGIZE2(...) #__VA_ARGS__
@@ -78,8 +75,6 @@
 #define INTERNAL_CATCH_MAKE_NAMESPACE2(...) ns_##__VA_ARGS__
 #define INTERNAL_CATCH_MAKE_NAMESPACE(name) INTERNAL_CATCH_MAKE_NAMESPACE2(name)
 
-#define INTERNAL_CATCH_REMOVE_PARENS(...) INTERNAL_CATCH_EXPAND1(INTERNAL_CATCH_DEF __VA_ARGS__)
-
 #ifndef CATCH_CONFIG_TRADITIONAL_MSVC_PREPROCESSOR
 #define INTERNAL_CATCH_MAKE_TYPE_LIST2(...) decltype(get_wrapper<INTERNAL_CATCH_REMOVE_PARENS_GEN(__VA_ARGS__)>())
 #define INTERNAL_CATCH_MAKE_TYPE_LIST(...) INTERNAL_CATCH_MAKE_TYPE_LIST2(INTERNAL_CATCH_REMOVE_PARENS(__VA_ARGS__))
diff --git a/src/catch2/internal/catch_preprocessor_remove_parens.hpp b/src/catch2/internal/catch_preprocessor_remove_parens.hpp
new file mode 100644
index 00000000..80337890
--- /dev/null
+++ b/src/catch2/internal/catch_preprocessor_remove_parens.hpp
@@ -0,0 +1,19 @@
+
+//              Copyright Catch2 Authors
+// Distributed under the Boost Software License, Version 1.0.
+//   (See accompanying file LICENSE_1_0.txt or copy at
+//        https://www.boost.org/LICENSE_1_0.txt)
+
+// SPDX-License-Identifier: BSL-1.0
+#ifndef CATCH_PREPROCESSOR_REMOVE_PARENS_HPP_INCLUDED
+#define CATCH_PREPROCESSOR_REMOVE_PARENS_HPP_INCLUDED
+
+#define INTERNAL_CATCH_EXPAND1( param ) INTERNAL_CATCH_EXPAND2( param )
+#define INTERNAL_CATCH_EXPAND2( ... ) INTERNAL_CATCH_NO##__VA_ARGS__
+#define INTERNAL_CATCH_DEF( ... ) INTERNAL_CATCH_DEF __VA_ARGS__
+#define INTERNAL_CATCH_NOINTERNAL_CATCH_DEF
+
+#define INTERNAL_CATCH_REMOVE_PARENS( ... ) \
+    INTERNAL_CATCH_EXPAND1( INTERNAL_CATCH_DEF __VA_ARGS__ )
+
+#endif // CATCH_PREPROCESSOR_REMOVE_PARENS_HPP_INCLUDED
diff --git a/src/catch2/internal/catch_reporter_spec_parser.cpp b/src/catch2/internal/catch_reporter_spec_parser.cpp
index 378a6f5a..28b2088a 100644
--- a/src/catch2/internal/catch_reporter_spec_parser.cpp
+++ b/src/catch2/internal/catch_reporter_spec_parser.cpp
@@ -12,7 +12,6 @@
 #include <catch2/internal/catch_move_and_forward.hpp>
 
 #include <algorithm>
-#include <ostream>
 
 namespace Catch {
 
diff --git a/src/catch2/internal/catch_tag_alias_registry.hpp b/src/catch2/internal/catch_tag_alias_registry.hpp
index 9dd86c13..3dbe0528 100644
--- a/src/catch2/internal/catch_tag_alias_registry.hpp
+++ b/src/catch2/internal/catch_tag_alias_registry.hpp
@@ -15,6 +15,7 @@
 #include <string>
 
 namespace Catch {
+    struct SourceLineInfo;
 
     class TagAliasRegistry : public ITagAliasRegistry {
     public:
diff --git a/src/catch2/internal/catch_test_registry.hpp b/src/catch2/internal/catch_test_registry.hpp
index cd28dd66..60508465 100644
--- a/src/catch2/internal/catch_test_registry.hpp
+++ b/src/catch2/internal/catch_test_registry.hpp
@@ -15,6 +15,7 @@
 #include <catch2/internal/catch_stringref.hpp>
 #include <catch2/internal/catch_unique_ptr.hpp>
 #include <catch2/internal/catch_unique_name.hpp>
+#include <catch2/internal/catch_preprocessor_remove_parens.hpp>
 
 // GCC 5 and older do not properly handle disabling unused-variable warning
 // with a _Pragma. This means that we have to leak the suppression to the
diff --git a/src/catch2/internal/catch_xmlwriter.hpp b/src/catch2/internal/catch_xmlwriter.hpp
index 5be8277d..edeb64a2 100644
--- a/src/catch2/internal/catch_xmlwriter.hpp
+++ b/src/catch2/internal/catch_xmlwriter.hpp
@@ -11,6 +11,7 @@
 #include <catch2/internal/catch_stream.hpp>
 #include <catch2/internal/catch_stringref.hpp>
 
+#include <iosfwd>
 #include <vector>
 
 namespace Catch {
diff --git a/src/catch2/reporters/catch_reporter_automake.hpp b/src/catch2/reporters/catch_reporter_automake.hpp
index c544f337..cd85e6bf 100644
--- a/src/catch2/reporters/catch_reporter_automake.hpp
+++ b/src/catch2/reporters/catch_reporter_automake.hpp
@@ -10,6 +10,8 @@
 
 #include <catch2/reporters/catch_reporter_streaming_base.hpp>
 
+#include <string>
+
 namespace Catch {
 
     class AutomakeReporter final : public StreamingReporterBase {
diff --git a/src/catch2/reporters/catch_reporter_cumulative_base.cpp b/src/catch2/reporters/catch_reporter_cumulative_base.cpp
index b52ba7ef..957880d0 100644
--- a/src/catch2/reporters/catch_reporter_cumulative_base.cpp
+++ b/src/catch2/reporters/catch_reporter_cumulative_base.cpp
@@ -7,6 +7,8 @@
 // SPDX-License-Identifier: BSL-1.0
 #include <catch2/reporters/catch_reporter_cumulative_base.hpp>
 
+#include <catch2/internal/catch_move_and_forward.hpp>
+
 #include <algorithm>
 #include <cassert>
 
diff --git a/src/catch2/reporters/catch_reporter_cumulative_base.hpp b/src/catch2/reporters/catch_reporter_cumulative_base.hpp
index d43ca479..742eaac9 100644
--- a/src/catch2/reporters/catch_reporter_cumulative_base.hpp
+++ b/src/catch2/reporters/catch_reporter_cumulative_base.hpp
@@ -12,7 +12,6 @@
 #include <catch2/internal/catch_unique_ptr.hpp>
 #include <catch2/internal/catch_optional.hpp>
 
-#include <iosfwd>
 #include <string>
 #include <vector>
 
diff --git a/src/catch2/reporters/catch_reporter_multi.cpp b/src/catch2/reporters/catch_reporter_multi.cpp
index 86d39d6a..e8cf7bdf 100644
--- a/src/catch2/reporters/catch_reporter_multi.cpp
+++ b/src/catch2/reporters/catch_reporter_multi.cpp
@@ -11,8 +11,6 @@
 #include <catch2/internal/catch_move_and_forward.hpp>
 #include <catch2/internal/catch_stream.hpp>
 
-#include <cassert>
-
 namespace Catch {
     void MultiReporter::updatePreferences(IEventListener const& reporterish) {
         m_preferences.shouldRedirectStdOut |=
diff --git a/src/catch2/reporters/catch_reporter_streaming_base.hpp b/src/catch2/reporters/catch_reporter_streaming_base.hpp
index afa67d76..5088bd0b 100644
--- a/src/catch2/reporters/catch_reporter_streaming_base.hpp
+++ b/src/catch2/reporters/catch_reporter_streaming_base.hpp
@@ -10,8 +10,6 @@
 
 #include <catch2/reporters/catch_reporter_common_base.hpp>
 
-#include <iosfwd>
-#include <string>
 #include <vector>
 
 namespace Catch {
diff --git a/src/catch2/reporters/catch_reporter_tap.cpp b/src/catch2/reporters/catch_reporter_tap.cpp
index 4cc91b7b..71249f87 100644
--- a/src/catch2/reporters/catch_reporter_tap.cpp
+++ b/src/catch2/reporters/catch_reporter_tap.cpp
@@ -11,6 +11,7 @@
 #include <catch2/catch_test_case_info.hpp>
 
 #include <algorithm>
+#include <iterator>
 #include <ostream>
 
 namespace Catch {
diff --git a/src/catch2/reporters/catch_reporter_teamcity.cpp b/src/catch2/reporters/catch_reporter_teamcity.cpp
index 8f16757a..142dffbb 100644
--- a/src/catch2/reporters/catch_reporter_teamcity.cpp
+++ b/src/catch2/reporters/catch_reporter_teamcity.cpp
@@ -14,6 +14,7 @@
 #include <catch2/catch_test_case_info.hpp>
 
 #include <cassert>
+#include <ostream>
 
 namespace Catch {
 
diff --git a/tests/ExtraTests/X05-DeferredStaticChecks.cpp b/tests/ExtraTests/X05-DeferredStaticChecks.cpp
index a09ed1cc..62ceb4a7 100644
--- a/tests/ExtraTests/X05-DeferredStaticChecks.cpp
+++ b/tests/ExtraTests/X05-DeferredStaticChecks.cpp
@@ -12,7 +12,6 @@
  */
 
 #include <catch2/catch_test_macros.hpp>
-#include <iostream>
 
 TEST_CASE("Deferred static checks") {
     STATIC_CHECK(1 == 2);