diff --git a/aegisub/src/aegisublocale.cpp b/aegisub/src/aegisublocale.cpp
index 90d162a76..beece3a02 100644
--- a/aegisub/src/aegisublocale.cpp
+++ b/aegisub/src/aegisublocale.cpp
@@ -38,8 +38,8 @@
 
 #ifndef AGI_PRE
 #include <algorithm>
+#include <clocale>
 #include <functional>
-#include <locale.h>
 
 #include <wx/dir.h>
 #include <wx/filename.h>
diff --git a/aegisub/src/ass_style.cpp b/aegisub/src/ass_style.cpp
index 503f0d06b..e38a2d129 100644
--- a/aegisub/src/ass_style.cpp
+++ b/aegisub/src/ass_style.cpp
@@ -35,7 +35,7 @@
 #include "config.h"
 
 #ifndef AGI_PRE
-#include <ctype.h>
+#include <cctype>
 
 #include <wx/intl.h>
 #include <wx/tokenzr.h>
diff --git a/aegisub/src/audio_box.cpp b/aegisub/src/audio_box.cpp
index c823db567..4c1b7fa51 100644
--- a/aegisub/src/audio_box.cpp
+++ b/aegisub/src/audio_box.cpp
@@ -35,7 +35,7 @@
 #include "config.h"
 
 #ifndef AGI_PRE
-#include <math.h>
+#include <cmath>
 
 #include <wx/bmpbuttn.h>
 #include <wx/panel.h>
diff --git a/aegisub/src/audio_controller.h b/aegisub/src/audio_controller.h
index 6aec8a203..de91dd25f 100644
--- a/aegisub/src/audio_controller.h
+++ b/aegisub/src/audio_controller.h
@@ -34,11 +34,12 @@
 #pragma once
 
 #ifndef AGI_PRE
-#include <memory>
-#include <vector>
-#include <set>
+#include <cassert>
 #include <cstdint>
-#include <assert.h>
+#include <memory>
+#include <set>
+#include <vector>
+
 #include <wx/event.h>
 #include <wx/string.h>
 #include <wx/timer.h>
diff --git a/aegisub/src/audio_provider_avs.cpp b/aegisub/src/audio_provider_avs.cpp
index 4674d587a..cde51e340 100644
--- a/aegisub/src/audio_provider_avs.cpp
+++ b/aegisub/src/audio_provider_avs.cpp
@@ -38,7 +38,7 @@
 
 #ifndef AGI_PRE
 #include <Mmreg.h>
-#include <time.h>
+#include <ctime>
 
 #include <wx/filename.h>
 #endif
diff --git a/aegisub/src/audio_provider_pcm.cpp b/aegisub/src/audio_provider_pcm.cpp
index fbc753736..375015c6c 100644
--- a/aegisub/src/audio_provider_pcm.cpp
+++ b/aegisub/src/audio_provider_pcm.cpp
@@ -36,7 +36,7 @@
 #include "config.h"
 
 #ifndef AGI_PRE
-#include <assert.h>
+#include <cassert>
 #include <cstdint>
 #ifndef __WINDOWS__
 #include <sys/fcntl.h>
diff --git a/aegisub/src/auto4_lua_assfile.cpp b/aegisub/src/auto4_lua_assfile.cpp
index 1e1f98866..0c5285bda 100644
--- a/aegisub/src/auto4_lua_assfile.cpp
+++ b/aegisub/src/auto4_lua_assfile.cpp
@@ -37,9 +37,9 @@
 #ifdef WITH_AUTO4_LUA
 
 #ifndef AGI_PRE
-#include <assert.h>
-
 #include <algorithm>
+#include <cassert>
+
 #include <boost/range/adaptor/indirected.hpp>
 #include <boost/range/algorithm_ext.hpp>
 
diff --git a/aegisub/src/charset_conv.cpp b/aegisub/src/charset_conv.cpp
index 7cadf1dae..2fec8cca1 100644
--- a/aegisub/src/charset_conv.cpp
+++ b/aegisub/src/charset_conv.cpp
@@ -37,7 +37,7 @@
 #include "charset_conv.h"
 
 #ifndef AGI_PRE
-#include <errno.h>
+#include <cerrno>
 #include <cstdint>
 
 #include <wx/intl.h>
diff --git a/aegisub/src/dialog_colorpicker.cpp b/aegisub/src/dialog_colorpicker.cpp
index 9ddab36a8..5fac7554f 100644
--- a/aegisub/src/dialog_colorpicker.cpp
+++ b/aegisub/src/dialog_colorpicker.cpp
@@ -35,7 +35,7 @@
 #include "config.h"
 
 #ifndef AGI_PRE
-#include <stdio.h>
+#include <cstdio>
 #include <vector>
 
 #include <wx/bitmap.h>
diff --git a/aegisub/src/fft.cpp b/aegisub/src/fft.cpp
index ac321ef7e..cde7de0fe 100644
--- a/aegisub/src/fft.cpp
+++ b/aegisub/src/fft.cpp
@@ -34,13 +34,10 @@
 /// Most of this code was taken from http://www.codeproject.com/audio/waveInFFT.asp
 /// And rewriten by Rodrigo Braz Monteiro
 
-
-///////////
-// Headers
 #include "config.h"
 
 #ifndef AGI_PRE
-#include <math.h>
+#include <cmath>
 #endif
 
 #include "fft.h"
diff --git a/aegisub/src/mkv_wrap.cpp b/aegisub/src/mkv_wrap.cpp
index bda73da27..5bb1850ba 100644
--- a/aegisub/src/mkv_wrap.cpp
+++ b/aegisub/src/mkv_wrap.cpp
@@ -35,11 +35,10 @@
 #include "config.h"
 
 #ifndef AGI_PRE
-#include <errno.h>
-#include <cstdint>
-#include <stdio.h>
-
 #include <algorithm>
+#include <cerrno>
+#include <cstdint>
+#include <cstdio>
 #include <iterator>
 
 #include <wx/filename.h>
diff --git a/aegisub/src/subtitle_format_transtation.cpp b/aegisub/src/subtitle_format_transtation.cpp
index b46d1aec6..cdd7f9bc0 100644
--- a/aegisub/src/subtitle_format_transtation.cpp
+++ b/aegisub/src/subtitle_format_transtation.cpp
@@ -35,7 +35,7 @@
 #include "config.h"
 
 #ifndef AGI_PRE
-#include <stdio.h>
+#include <cstdio>
 #endif
 
 #include "subtitle_format_transtation.h"
diff --git a/aegisub/src/text_file_reader.cpp b/aegisub/src/text_file_reader.cpp
index c5c501116..a13aaf721 100644
--- a/aegisub/src/text_file_reader.cpp
+++ b/aegisub/src/text_file_reader.cpp
@@ -35,10 +35,9 @@
 #include "config.h"
 
 #ifndef AGI_PRE
-#include <assert.h>
-#include <errno.h>
-
 #include <algorithm>
+#include <cassert>
+#include <cerrno>
 #include <string>
 
 #include <wx/string.h>
diff --git a/aegisub/src/video_context.cpp b/aegisub/src/video_context.cpp
index f1814508a..cbdc4aa62 100644
--- a/aegisub/src/video_context.cpp
+++ b/aegisub/src/video_context.cpp
@@ -35,7 +35,7 @@
 #include "config.h"
 
 #ifndef AGI_PRE
-#include <string.h>
+#include <cstring>
 
 #include <wx/clipbrd.h>
 #include <wx/config.h>
diff --git a/aegisub/src/video_provider_yuv4mpeg.h b/aegisub/src/video_provider_yuv4mpeg.h
index b2479fc31..02d91d649 100644
--- a/aegisub/src/video_provider_yuv4mpeg.h
+++ b/aegisub/src/video_provider_yuv4mpeg.h
@@ -34,7 +34,7 @@
 
 #include "include/aegisub/video_provider.h"
 #ifndef AGI_PRE
-#include <stdio.h>
+#include <cstdio>
 
 #include <vector>