Index: source/gui/CGUIText.cpp
===================================================================
--- source/gui/CGUIText.cpp
+++ source/gui/CGUIText.cpp
@@ -429,6 +429,10 @@
 
 void CGUIText::Draw(CGUI& pGUI, const CGUIColor& DefaultColor, const CPos& pos, const float z, const CRect& clipping) const
 {
+#ifndef NDEBUG
+	ogl_DebugGroup group("Draw GUI text");
+#endif
+
 	CShaderTechniquePtr tech = g_Renderer.GetShaderManager().LoadEffect(str_gui_text);
 
 	tech->BeginPass();
Index: source/gui/GUIRenderer.cpp
===================================================================
--- source/gui/GUIRenderer.cpp
+++ source/gui/GUIRenderer.cpp
@@ -337,6 +337,10 @@
 
 	// TODO: batching by shader/texture/etc would be nice
 
+#ifndef NDEBUG
+	ogl_DebugGroup group("Draw GUI element");
+#endif
+
 	CMatrix3D matrix = GetDefaultGuiMatrix();
 
 	glDisable(GL_BLEND);
Index: source/gui/ObjectTypes/CMiniMap.cpp
===================================================================
--- source/gui/ObjectTypes/CMiniMap.cpp
+++ source/gui/ObjectTypes/CMiniMap.cpp
@@ -380,6 +380,9 @@
 void CMiniMap::Draw()
 {
 	PROFILE3("render minimap");
+#ifndef NDEBUG
+	ogl_DebugGroup group("Render minimap");
+#endif
 
 	// The terrain isn't actually initialized until the map is loaded, which
 	// happens when the game is started, so abort until then.
Index: source/lib/external_libraries/glext_funcs.h
===================================================================
--- source/lib/external_libraries/glext_funcs.h
+++ source/lib/external_libraries/glext_funcs.h
@@ -1,4 +1,4 @@
-/* Copyright (C) 2013 Wildfire Games.
+/* Copyright (C) 2019 Wildfire Games.
  *
  * Permission is hereby granted, free of charge, to any person obtaining
  * a copy of this software and associated documentation files (the
@@ -125,10 +125,26 @@
 
 typedef GLuint GLhandleARB;
 
+// GL_KHR_debug / GLES3.2
+typedef void (GL_APIENTRY  *GLDEBUGPROCKHR)(GLenum source, GLenum type, GLuint id, GLenum severity, GLsizei length, const GLchar *message, const void *userParam);
+FUNC2(void, glDebugMessageCallbackKHR, glDebugMessageCallback, "3.2", (GLDEBUGPROCKHR callback, const GLvoid* userParam))
+FUNC2(void, glDebugMessageControlKHR, glDebugMessageControl, "3.2", (GLenum source, GLenum type, GLenum severity, GLsizei count, const GLuint* ids, GLboolean enabled))
+FUNC2(void, glPushDebugGroupKHR, glPushDebugGroup, "3.2", (GLenum source, GLuint id, GLsizei length, const GLchar* message))
+FUNC2(void, glPopDebugGroupKHR, glPopDebugGroup, "3.2", (void))
+FUNC2(void, glObjectLabelKHR, glObjectLabel, "3.2", (GLenum identifier, GLuint name, GLsizei length, const GLchar* label))
+
 #else
 
 // were these defined as real functions in gl.h already?
 
+// GL_KHR_debug / GL4.3
+typedef void (APIENTRY  *GLDEBUGPROC)(GLenum source, GLenum type, GLuint id, GLenum severity, GLsizei length, const GLchar *message, const void *userParam);
+FUNC2(void, glDebugMessageCallbackKHR, glDebugMessageCallback, "4.3", (GLDEBUGPROC callback, const GLvoid* userParam))
+FUNC2(void, glDebugMessageControlKHR, glDebugMessageControl, "4.3", (GLenum source, GLenum type, GLenum severity, GLsizei count, const GLuint* ids, GLboolean enabled))
+FUNC2(void, glPushDebugGroupKHR, glPushDebugGroup, "4.3", (GLenum source, GLuint id, GLsizei length, const GLchar* message))
+FUNC2(void, glPopDebugGroupKHR, glPopDebugGroup, "4.3", (void))
+FUNC2(void, glObjectLabelKHR, glObjectLabel, "4.3", (GLenum identifier, GLuint name, GLsizei length, const GLchar *label))
+
 // GL_EXT_draw_range_elements / GL1.2:
 FUNC2(void, glDrawRangeElementsEXT, glDrawRangeElements, "1.2", (GLenum, GLuint, GLuint, GLsizei, GLenum, GLvoid*))
 
Index: source/lib/ogl.h
===================================================================
--- source/lib/ogl.h
+++ source/lib/ogl.h
@@ -191,4 +191,23 @@
 extern GLint ogl_max_tex_size;				/// [pixels]
 extern GLint ogl_max_tex_units;				/// limit on GL_TEXTUREn
 
+#ifndef NDEBUG
+/**
+ * RAII for glPushDebugGroupKHR() and pglPopDebugGroupKHR().
+ */
+class ogl_DebugGroup
+{
+public:
+	ogl_DebugGroup(const char* message)
+	{
+		pglPushDebugGroupKHR(GL_DEBUG_SOURCE_APPLICATION, 0x0ad, -1, message);
+	}
+
+	~ogl_DebugGroup()
+	{
+		pglPopDebugGroupKHR();
+	}
+};
+#endif
+
 #endif	// #ifndef INCLUDED_OGL
Index: source/lib/ogl.cpp
===================================================================
--- source/lib/ogl.cpp
+++ source/lib/ogl.cpp
@@ -421,6 +421,84 @@
 		debug_printf("%s:%d: OpenGL error(s) occurred: %s (%04x)\n", file, line, ogl_GetErrorName(first_error), (unsigned int)first_error);
 }
 
+void ogl_OnDebugMessage(GLenum source, GLenum type, GLuint id, GLenum severity, GLsizei UNUSED(length), const GLchar* message, const void* UNUSED(user_param))
+{
+	std::string str_source = "unknown";
+	std::string str_type = "unknown";
+	std::string str_severity = "unknown";
+
+	switch (source)
+	{
+		case GL_DEBUG_SOURCE_API:
+			str_source = "the API";
+			break;
+		case GL_DEBUG_SOURCE_WINDOW_SYSTEM:
+			str_source = "the window system";
+			break;
+		case GL_DEBUG_SOURCE_SHADER_COMPILER:
+			str_source = "the shader compiler";
+			break;
+		case GL_DEBUG_SOURCE_THIRD_PARTY:
+			str_source = "a third party";
+			break;
+		case GL_DEBUG_SOURCE_APPLICATION:
+			str_source = "the application";
+			break;
+		case GL_DEBUG_SOURCE_OTHER:
+			str_source = "somewhere";
+			break;
+	}
+
+	switch (type)
+	{
+		case GL_DEBUG_TYPE_ERROR:
+			str_type = "error";
+			break;
+		case GL_DEBUG_TYPE_DEPRECATED_BEHAVIOR:
+			str_type = "deprecated behaviour";
+			break;
+		case GL_DEBUG_TYPE_UNDEFINED_BEHAVIOR:
+			str_type = "undefined behaviour";
+			break;
+		case GL_DEBUG_TYPE_PORTABILITY:
+			str_type = "portability";
+			break;
+		case GL_DEBUG_TYPE_PERFORMANCE:
+			str_type = "performance";
+			break;
+		case GL_DEBUG_TYPE_OTHER:
+			str_type = "other";
+			break;
+		case GL_DEBUG_TYPE_MARKER:
+			str_type = "marker";
+			break;
+		case GL_DEBUG_TYPE_PUSH_GROUP:
+			str_type = "push group";
+			break;
+		case GL_DEBUG_TYPE_POP_GROUP:
+			str_type = "pop group";
+			break;
+	}
+
+	switch (severity)
+	{
+		case GL_DEBUG_SEVERITY_HIGH:
+			str_severity = "high";
+			break;
+		case GL_DEBUG_SEVERITY_MEDIUM:
+			str_severity = "medium";
+			break;
+		case GL_DEBUG_SEVERITY_LOW:
+			str_severity = "low";
+			break;
+		case GL_DEBUG_SEVERITY_NOTIFICATION:
+			str_severity = "notification";
+			break;
+	}
+
+	debug_printf("OpenGL %s of severity %s from %s id %d: %s\n", str_type.c_str(), str_severity.c_str(), str_source.c_str(), id, message);
+}
+
 
 // ignore and reset the specified error (as returned by glGetError).
 // any other errors that have occurred are reported as ogl_WarnIfError would.
@@ -492,4 +570,22 @@
 #if !CONFIG2_GLES
 	glGetIntegerv(GL_MAX_TEXTURE_UNITS, &ogl_max_tex_units);
 #endif
+
+#ifndef NDEBUG
+#if CONFIG2_GLES
+	bool is_core = ogl_HaveVersion("3.2");
+#else
+	bool is_core = ogl_HaveVersion("4.3");
+#endif
+	if (is_core || ogl_HaveExtension("GL_KHR_debug"))
+	{
+		glEnable(GL_DEBUG_OUTPUT);
+		pglDebugMessageCallbackKHR(ogl_OnDebugMessage, nullptr);
+
+		// Filter out our own debug group messages
+		GLuint id = 0x0ad;
+		pglDebugMessageControlKHR(GL_DEBUG_SOURCE_APPLICATION, GL_DEBUG_TYPE_PUSH_GROUP, GL_DONT_CARE, 1, &id, GL_FALSE);
+		pglDebugMessageControlKHR(GL_DEBUG_SOURCE_APPLICATION, GL_DEBUG_TYPE_POP_GROUP, GL_DONT_CARE, 1, &id, GL_FALSE);
+	}
+#endif
 }
Index: source/lib/res/graphics/ogl_tex.cpp
===================================================================
--- source/lib/res/graphics/ogl_tex.cpp
+++ source/lib/res/graphics/ogl_tex.cpp
@@ -480,6 +480,12 @@
 	if(ot->flags & OT_NEED_AUTO_UPLOAD)
 		(void)ogl_tex_upload(h);
 
+#ifndef NDEBUG
+	std::string name = pathname.string8();
+	glBindTexture(GL_TEXTURE_2D, ot->id);
+	pglObjectLabelKHR(GL_TEXTURE, ot->id, name.size(), name.c_str());
+#endif
+
 	return INFO::OK;
 }
 
Index: source/ps/CLogger.cpp
===================================================================
--- source/ps/CLogger.cpp
+++ source/ps/CLogger.cpp
@@ -202,6 +202,9 @@
 void CLogger::Render()
 {
 	PROFILE3_GPU("logger");
+#ifndef NDEBUG
+	ogl_DebugGroup group("Draw CLogger messages");
+#endif
 
 	CleanupRenderQueue();
 
Index: source/renderer/Renderer.cpp
===================================================================
--- source/renderer/Renderer.cpp
+++ source/renderer/Renderer.cpp
@@ -724,6 +724,9 @@
 void CRenderer::RenderShadowMap(const CShaderDefines& context)
 {
 	PROFILE3_GPU("shadow map");
+#ifndef NDEBUG
+	ogl_DebugGroup group("Render shadow map");
+#endif
 
 	m->shadow.BeginRender();
 
@@ -759,6 +762,9 @@
 void CRenderer::RenderPatches(const CShaderDefines& context, int cullGroup)
 {
 	PROFILE3_GPU("patches");
+#ifndef NDEBUG
+	ogl_DebugGroup group("Render patches");
+#endif
 
 #if CONFIG2_GLES
 #warning TODO: implement wireface/edged rendering mode GLES
@@ -815,6 +821,9 @@
 void CRenderer::RenderModels(const CShaderDefines& context, int cullGroup)
 {
 	PROFILE3_GPU("models");
+#ifndef NDEBUG
+	ogl_DebugGroup group("Render models");
+#endif
 
 	int flags = 0;
 
@@ -850,6 +859,9 @@
 void CRenderer::RenderTransparentModels(const CShaderDefines& context, int cullGroup, ETransparentMode transparentMode, bool disableFaceCulling)
 {
 	PROFILE3_GPU("transparent models");
+#ifndef NDEBUG
+	ogl_DebugGroup group("Render transparent models");
+#endif
 
 	int flags = 0;
 
@@ -1019,6 +1031,9 @@
 void CRenderer::RenderReflections(const CShaderDefines& context, const CBoundingBoxAligned& scissor)
 {
 	PROFILE3_GPU("water reflections");
+#ifndef NDEBUG
+	ogl_DebugGroup group("Render water reflections");
+#endif
 
 	// Save the post-processing framebuffer.
 	GLint fbo;
@@ -1089,8 +1104,6 @@
 
 	// rebind post-processing frambuffer.
 	pglBindFramebufferEXT(GL_FRAMEBUFFER_EXT, fbo);
-
-	return;
 }
 
 
@@ -1099,6 +1112,9 @@
 void CRenderer::RenderRefractions(const CShaderDefines& context, const CBoundingBoxAligned &scissor)
 {
 	PROFILE3_GPU("water refractions");
+#ifndef NDEBUG
+	ogl_DebugGroup group("Render water refractions");
+#endif
 
 	// Save the post-processing framebuffer.
 	GLint fbo;
@@ -1153,13 +1169,14 @@
 
 	// rebind post-processing frambuffer.
 	pglBindFramebufferEXT(GL_FRAMEBUFFER_EXT, fbo);
-
-	return;
 }
 
 void CRenderer::RenderSilhouettes(const CShaderDefines& context)
 {
 	PROFILE3_GPU("silhouettes");
+#ifndef NDEBUG
+	ogl_DebugGroup group("Render silhouettes");
+#endif
 
 	CShaderDefines contextOccluder = context;
 	contextOccluder.Add(str_MODE_SILHOUETTEOCCLUDER, str_1);
@@ -1265,6 +1282,9 @@
 		return;
 
 	PROFILE3_GPU("particles");
+#ifndef NDEBUG
+	ogl_DebugGroup group("Render particles");
+#endif
 
 	m->particleRenderer.RenderParticles(cullGroup);
 
@@ -1298,6 +1318,9 @@
 void CRenderer::RenderSubmissions(const CBoundingBoxAligned& waterScissor)
 {
 	PROFILE3("render submissions");
+#ifndef NDEBUG
+	ogl_DebugGroup group("Render submissions");
+#endif
 
 	GetScene().GetLOSTexture().InterpolateLOS();
 
@@ -1454,7 +1477,6 @@
 	// render overlays that should appear on top of all other objects
 	m->overlayRenderer.RenderForegroundOverlays(m_ViewCamera);
 	ogl_WarnIfError();
-
 }
 
 ///////////////////////////////////////////////////////////////////////////////////////////////////
Index: source/renderer/SkyManager.cpp
===================================================================
--- source/renderer/SkyManager.cpp
+++ source/renderer/SkyManager.cpp
@@ -58,6 +58,11 @@
 		L"top",
 		L"top"
 	};
+
+#ifndef NDEBUG
+	ogl_DebugGroup group("Load sky textures");
+#endif
+
 	/*for (size_t i = 0; i < ARRAY_SIZE(m_SkyTexture); ++i)
 	{
 		VfsPath path = VfsPath("art/textures/skies") / m_SkySet / (Path::String(s_imageNames[i])+L".dds");
@@ -144,7 +149,6 @@
 	glTexParameteri(GL_TEXTURE_CUBE_MAP, GL_TEXTURE_WRAP_R, GL_CLAMP_TO_EDGE);
 #endif
 	glBindTexture(GL_TEXTURE_CUBE_MAP, 0);
-	///////////////////////////////////////////////////////////////////////////
 }
 
 
@@ -193,6 +197,10 @@
 // Render sky
 void SkyManager::RenderSky()
 {
+#ifndef NDEBUG
+	ogl_DebugGroup group("Render sky");
+#endif
+
 #if CONFIG2_GLES
 #warning TODO: implement SkyManager::RenderSky for GLES
 #else
Index: source/renderer/TerrainRenderer.cpp
===================================================================
--- source/renderer/TerrainRenderer.cpp
+++ source/renderer/TerrainRenderer.cpp
@@ -631,6 +631,9 @@
 bool TerrainRenderer::RenderFancyWater(const CShaderDefines& context, int cullGroup, ShadowMap* shadow)
 {
 	PROFILE3_GPU("fancy water");
+#ifndef NDEBUG
+	ogl_DebugGroup group("Render fancy water");
+#endif
 
 	WaterManager* WaterMgr = g_Renderer.GetWaterManager();
 	CShaderDefines defines = context;
@@ -842,6 +845,10 @@
 
 void TerrainRenderer::RenderSimpleWater(int cullGroup)
 {
+#ifndef NDEBUG
+	ogl_DebugGroup group("Render simple water");
+#endif
+
 #if CONFIG2_GLES
 	UNUSED2(cullGroup);
 #else
Index: source/renderer/WaterManager.cpp
===================================================================
--- source/renderer/WaterManager.cpp
+++ source/renderer/WaterManager.cpp
@@ -481,6 +481,10 @@
 // This requires m_DistanceHeightmap to be defined properly.
 void WaterManager::CreateWaveMeshes()
 {
+#ifndef NDEBUG
+	ogl_DebugGroup group("Create wave meshes");
+#endif
+
 	if (m_MapSize == 0)
 		return;
 
@@ -876,6 +880,10 @@
 	if (g_Renderer.m_SkipSubmit || !m_WaterFancyEffects)
 		return;
 
+#ifndef NDEBUG
+	ogl_DebugGroup group("Render waves");
+#endif
+
 	pglBindFramebufferEXT(GL_FRAMEBUFFER_EXT, m_FancyEffectsFBO);
 
 	GLuint attachments[2] = { GL_COLOR_ATTACHMENT0_EXT, GL_COLOR_ATTACHMENT1_EXT };