diff --git a/include/yaml-cpp/emitfromevents.h b/include/yaml-cpp/emitfromevents.h
index d760337..59300c5 100644
--- a/include/yaml-cpp/emitfromevents.h
+++ b/include/yaml-cpp/emitfromevents.h
@@ -7,9 +7,15 @@
 #pragma once
 #endif
 
-#include "yaml-cpp/eventhandler.h"
 #include <stack>
 
+#include "yaml-cpp/anchor.h"
+#include "yaml-cpp/eventhandler.h"
+
+namespace YAML {
+struct Mark;
+}  // namespace YAML
+
 namespace YAML {
 class Emitter;
 
diff --git a/include/yaml-cpp/emitter.h b/include/yaml-cpp/emitter.h
index 484fcc7..a8f56dc 100644
--- a/include/yaml-cpp/emitter.h
+++ b/include/yaml-cpp/emitter.h
@@ -7,16 +7,22 @@
 #pragma once
 #endif
 
-#include "yaml-cpp/dll.h"
+#include <memory>
+#include <sstream>
+#include <string>
+
 #include "yaml-cpp/binary.h"
+#include "yaml-cpp/dll.h"
 #include "yaml-cpp/emitterdef.h"
 #include "yaml-cpp/emittermanip.h"
 #include "yaml-cpp/noncopyable.h"
 #include "yaml-cpp/null.h"
 #include "yaml-cpp/ostream_wrapper.h"
-#include <memory>
-#include <string>
-#include <sstream>
+
+namespace YAML {
+class Binary;
+struct _Null;
+}  // namespace YAML
 
 namespace YAML {
 class EmitterState;
diff --git a/include/yaml-cpp/parser.h b/include/yaml-cpp/parser.h
index 18389bb..24880e4 100644
--- a/include/yaml-cpp/parser.h
+++ b/include/yaml-cpp/parser.h
@@ -7,16 +7,18 @@
 #pragma once
 #endif
 
-#include "yaml-cpp/dll.h"
-#include "yaml-cpp/noncopyable.h"
 #include <ios>
 #include <memory>
 
+#include "yaml-cpp/dll.h"
+#include "yaml-cpp/noncopyable.h"
+
 namespace YAML {
+class EventHandler;
+class Node;
+class Scanner;
 struct Directives;
 struct Token;
-class EventHandler;
-class Scanner;
 
 class YAML_CPP_API Parser : private noncopyable {
  public:
diff --git a/src/contrib/graphbuilder.cpp b/src/contrib/graphbuilder.cpp
index 9981e15..416c135 100644
--- a/src/contrib/graphbuilder.cpp
+++ b/src/contrib/graphbuilder.cpp
@@ -1,8 +1,10 @@
-#include "yaml-cpp/parser.h"
-#include "yaml-cpp/contrib/graphbuilder.h"
 #include "graphbuilderadapter.h"
 
+#include "yaml-cpp/parser.h"  // IWYU pragma: keep
+
 namespace YAML {
+class GraphBuilderInterface;
+
 void* BuildGraphOfNextDocument(Parser& parser,
                                GraphBuilderInterface& graphBuilder) {
   GraphBuilderAdapter eventHandler(graphBuilder);
diff --git a/src/contrib/graphbuilderadapter.cpp b/src/contrib/graphbuilderadapter.cpp
index 5967e88..663a9e9 100644
--- a/src/contrib/graphbuilderadapter.cpp
+++ b/src/contrib/graphbuilderadapter.cpp
@@ -1,6 +1,9 @@
 #include "graphbuilderadapter.h"
+#include "yaml-cpp/contrib/graphbuilder.h"
 
 namespace YAML {
+struct Mark;
+
 int GraphBuilderAdapter::ContainerFrame::sequenceMarker;
 
 void GraphBuilderAdapter::OnNull(const Mark &mark, anchor_t anchor) {
diff --git a/src/contrib/graphbuilderadapter.h b/src/contrib/graphbuilderadapter.h
index f331225..c54efa5 100644
--- a/src/contrib/graphbuilderadapter.h
+++ b/src/contrib/graphbuilderadapter.h
@@ -10,9 +10,16 @@
 #include <cstdlib>
 #include <map>
 #include <stack>
-#include "yaml-cpp/eventhandler.h"
+
+#include "yaml-cpp/anchor.h"
 #include "yaml-cpp/contrib/anchordict.h"
 #include "yaml-cpp/contrib/graphbuilder.h"
+#include "yaml-cpp/eventhandler.h"
+
+namespace YAML {
+class GraphBuilderInterface;
+struct Mark;
+}  // namespace YAML
 
 namespace YAML {
 class GraphBuilderAdapter : public EventHandler {
diff --git a/src/emitfromevents.cpp b/src/emitfromevents.cpp
index 4552ddd..baf39be 100644
--- a/src/emitfromevents.cpp
+++ b/src/emitfromevents.cpp
@@ -1,9 +1,15 @@
-#include "yaml-cpp/emitfromevents.h"
-#include "yaml-cpp/emitter.h"
-#include "yaml-cpp/null.h"
 #include <cassert>
 #include <sstream>
 
+#include "yaml-cpp/emitfromevents.h"
+#include "yaml-cpp/emitter.h"
+#include "yaml-cpp/emittermanip.h"
+#include "yaml-cpp/null.h"
+
+namespace YAML {
+struct Mark;
+}  // namespace YAML
+
 namespace {
 std::string ToString(YAML::anchor_t anchor) {
   std::stringstream stream;
diff --git a/src/emitter.cpp b/src/emitter.cpp
index d905517..c666901 100644
--- a/src/emitter.cpp
+++ b/src/emitter.cpp
@@ -1,11 +1,16 @@
-#include "yaml-cpp/emitter.h"
-#include "emitterstate.h"
-#include "emitterutils.h"
-#include "indentation.h"
-#include "yaml-cpp/exceptions.h"
 #include <sstream>
 
+#include "emitterutils.h"
+#include "indentation.h"  // IWYU pragma: keep
+#include "yaml-cpp/emitter.h"
+#include "yaml-cpp/emitterdef.h"
+#include "yaml-cpp/emittermanip.h"
+#include "yaml-cpp/exceptions.h"  // IWYU pragma: keep
+
 namespace YAML {
+class Binary;
+struct _Null;
+
 Emitter::Emitter() : m_pState(new EmitterState) {}
 
 Emitter::Emitter(std::ostream& stream)
diff --git a/src/emitterstate.cpp b/src/emitterstate.cpp
index 539994c..c99509f 100644
--- a/src/emitterstate.cpp
+++ b/src/emitterstate.cpp
@@ -1,7 +1,8 @@
-#include "emitterstate.h"
-#include "yaml-cpp/exceptions.h"
 #include <limits>
 
+#include "emitterstate.h"
+#include "yaml-cpp/exceptions.h"  // IWYU pragma: keep
+
 namespace YAML {
 EmitterState::EmitterState()
     : m_isGood(true),
diff --git a/src/emitterutils.cpp b/src/emitterutils.cpp
index 80d2740..7438bf6 100644
--- a/src/emitterutils.cpp
+++ b/src/emitterutils.cpp
@@ -1,11 +1,14 @@
+#include <iomanip>
+#include <sstream>
+
 #include "emitterutils.h"
 #include "exp.h"
 #include "indentation.h"
-#include "yaml-cpp/binary.h"
-#include "yaml-cpp/exceptions.h"
+#include "regex_yaml.h"
+#include "regeximpl.h"
 #include "stringsource.h"
-#include <sstream>
-#include <iomanip>
+#include "yaml-cpp/binary.h"  // IWYU pragma: keep
+#include "yaml-cpp/ostream_wrapper.h"
 
 namespace YAML {
 namespace Utils {
diff --git a/src/emitterutils.h b/src/emitterutils.h
index 398a02c..d80ccaa 100644
--- a/src/emitterutils.h
+++ b/src/emitterutils.h
@@ -7,10 +7,16 @@
 #pragma once
 #endif
 
-#include "emitterstate.h"
-#include "yaml-cpp/ostream_wrapper.h"
 #include <string>
 
+#include "emitterstate.h"
+#include "yaml-cpp/emittermanip.h"
+#include "yaml-cpp/ostream_wrapper.h"
+
+namespace YAML {
+class ostream_wrapper;
+}  // namespace YAML
+
 namespace YAML {
 class Binary;
 
diff --git a/src/exp.cpp b/src/exp.cpp
index 7986bf9..695440a 100644
--- a/src/exp.cpp
+++ b/src/exp.cpp
@@ -1,7 +1,13 @@
-#include "exp.h"
-#include "yaml-cpp/exceptions.h"
 #include <sstream>
 
+#include "exp.h"
+#include "stream.h"
+#include "yaml-cpp/exceptions.h"  // IWYU pragma: keep
+
+namespace YAML {
+struct Mark;
+}  // namespace YAML
+
 namespace YAML {
 namespace Exp {
 unsigned ParseHex(const std::string& str, const Mark& mark) {
diff --git a/src/exp.h b/src/exp.h
index 10eb27a..f248802 100644
--- a/src/exp.h
+++ b/src/exp.h
@@ -7,9 +7,10 @@
 #pragma once
 #endif
 
-#include "regex_yaml.h"
-#include <string>
 #include <ios>
+#include <string>
+
+#include "regex_yaml.h"
 #include "stream.h"
 
 namespace YAML {
diff --git a/src/parser.cpp b/src/parser.cpp
index 044c296..9310576 100644
--- a/src/parser.cpp
+++ b/src/parser.cpp
@@ -1,15 +1,16 @@
-#include "yaml-cpp/parser.h"
-#include "yaml-cpp/eventhandler.h"
-#include "yaml-cpp/exceptions.h"
-#include "directives.h"
-#include "scanner.h"
-#include "singledocparser.h"
-#include "tag.h"
-#include "token.h"
-#include <sstream>
 #include <cstdio>
+#include <sstream>
+
+#include "directives.h"  // IWYU pragma: keep
+#include "scanner.h"  // IWYU pragma: keep
+#include "singledocparser.h"
+#include "token.h"
+#include "yaml-cpp/exceptions.h"  // IWYU pragma: keep
+#include "yaml-cpp/parser.h"
 
 namespace YAML {
+class EventHandler;
+
 Parser::Parser() {}
 
 Parser::Parser(std::istream& in) { Load(in); }
diff --git a/src/regex_yaml.h b/src/regex_yaml.h
index 2177354..247e5a5 100644
--- a/src/regex_yaml.h
+++ b/src/regex_yaml.h
@@ -7,8 +7,8 @@
 #pragma once
 #endif
 
-#include <vector>
 #include <string>
+#include <vector>
 
 namespace YAML {
 class Stream;
diff --git a/src/scanner.cpp b/src/scanner.cpp
index 91272bb..82c1b2f 100644
--- a/src/scanner.cpp
+++ b/src/scanner.cpp
@@ -1,10 +1,11 @@
-#include "scanner.h"
-#include "token.h"
-#include "yaml-cpp/exceptions.h"
-#include "exp.h"
 #include <cassert>
 #include <memory>
 
+#include "exp.h"
+#include "scanner.h"
+#include "token.h"
+#include "yaml-cpp/exceptions.h"  // IWYU pragma: keep
+
 namespace YAML {
 Scanner::Scanner(std::istream& in)
     : INPUT(in),
diff --git a/src/scanner.h b/src/scanner.h
index 0643214..204259b 100644
--- a/src/scanner.h
+++ b/src/scanner.h
@@ -8,14 +8,16 @@
 #endif
 
 #include <ios>
-#include <string>
-#include <queue>
-#include <stack>
-#include <set>
 #include <map>
+#include <queue>
+#include <set>
+#include <stack>
+#include <string>
+
 #include "ptr_vector.h"
 #include "stream.h"
 #include "token.h"
+#include "yaml-cpp/mark.h"
 
 namespace YAML {
 class Node;
diff --git a/src/scanscalar.cpp b/src/scanscalar.cpp
index c09aca7..165742e 100644
--- a/src/scanscalar.cpp
+++ b/src/scanscalar.cpp
@@ -1,8 +1,8 @@
-#include "scanscalar.h"
-#include "scanner.h"
 #include "exp.h"
-#include "yaml-cpp/exceptions.h"
-#include "token.h"
+#include "regeximpl.h"
+#include "scanscalar.h"
+#include "stream.h"
+#include "yaml-cpp/exceptions.h"  // IWYU pragma: keep
 
 namespace YAML {
 // ScanScalar
diff --git a/src/scanscalar.h b/src/scanscalar.h
index 315476d..f7f369b 100644
--- a/src/scanscalar.h
+++ b/src/scanscalar.h
@@ -8,6 +8,7 @@
 #endif
 
 #include <string>
+
 #include "regex_yaml.h"
 #include "stream.h"
 
diff --git a/src/scantag.cpp b/src/scantag.cpp
index 471ac19..c5b3965 100644
--- a/src/scantag.cpp
+++ b/src/scantag.cpp
@@ -1,7 +1,9 @@
-#include "scanner.h"
-#include "regex_yaml.h"
 #include "exp.h"
-#include "yaml-cpp/exceptions.h"
+#include "regex_yaml.h"
+#include "regeximpl.h"
+#include "stream.h"
+#include "yaml-cpp/exceptions.h"  // IWYU pragma: keep
+#include "yaml-cpp/mark.h"
 
 namespace YAML {
 const std::string ScanVerbatimTag(Stream& INPUT) {
diff --git a/src/scantoken.cpp b/src/scantoken.cpp
index dc9396e..d941b68 100644
--- a/src/scantoken.cpp
+++ b/src/scantoken.cpp
@@ -1,12 +1,16 @@
-#include "scanner.h"
-#include "token.h"
-#include "yaml-cpp/exceptions.h"
-#include "exp.h"
-#include "scanscalar.h"
-#include "scantag.h"
-#include "tag.h"
 #include <sstream>
 
+#include "exp.h"
+#include "regex_yaml.h"
+#include "regeximpl.h"
+#include "scanner.h"
+#include "scanscalar.h"
+#include "scantag.h"  // IWYU pragma: keep
+#include "tag.h"  // IWYU pragma: keep
+#include "token.h"
+#include "yaml-cpp/exceptions.h"  // IWYU pragma: keep
+#include "yaml-cpp/mark.h"
+
 namespace YAML {
 ///////////////////////////////////////////////////////////////////////
 // Specialization for scanning specific tokens
diff --git a/src/simplekey.cpp b/src/simplekey.cpp
index 362bfc1..bec8720 100644
--- a/src/simplekey.cpp
+++ b/src/simplekey.cpp
@@ -1,9 +1,9 @@
 #include "scanner.h"
 #include "token.h"
-#include "yaml-cpp/exceptions.h"
-#include "exp.h"
 
 namespace YAML {
+struct Mark;
+
 Scanner::SimpleKey::SimpleKey(const Mark& mark_, int flowLevel_)
     : mark(mark_), flowLevel(flowLevel_), pIndent(0), pMapStart(0), pKey(0) {}
 
diff --git a/src/singledocparser.cpp b/src/singledocparser.cpp
index 918ff85..ad72421 100644
--- a/src/singledocparser.cpp
+++ b/src/singledocparser.cpp
@@ -1,14 +1,15 @@
-#include "singledocparser.h"
-#include "collectionstack.h"
-#include "directives.h"
-#include "yaml-cpp/eventhandler.h"
-#include "yaml-cpp/exceptions.h"
+#include <algorithm>
+#include <cstdio>
+#include <sstream>
+
+#include "collectionstack.h"  // IWYU pragma: keep
 #include "scanner.h"
+#include "singledocparser.h"
 #include "tag.h"
 #include "token.h"
-#include <sstream>
-#include <cstdio>
-#include <algorithm>
+#include "yaml-cpp/eventhandler.h"
+#include "yaml-cpp/exceptions.h"  // IWYU pragma: keep
+#include "yaml-cpp/mark.h"
 
 namespace YAML {
 SingleDocParser::SingleDocParser(Scanner& scanner, const Directives& directives)
diff --git a/src/singledocparser.h b/src/singledocparser.h
index d4d605b..ed0aad5 100644
--- a/src/singledocparser.h
+++ b/src/singledocparser.h
@@ -7,20 +7,21 @@
 #pragma once
 #endif
 
-#include "yaml-cpp/anchor.h"
-#include "yaml-cpp/noncopyable.h"
-#include <string>
 #include <map>
 #include <memory>
+#include <string>
+
+#include "yaml-cpp/anchor.h"
+#include "yaml-cpp/noncopyable.h"
 
 namespace YAML {
-struct Directives;
-struct Mark;
-struct Token;
 class CollectionStack;
 class EventHandler;
 class Node;
 class Scanner;
+struct Directives;
+struct Mark;
+struct Token;
 
 class SingleDocParser : private noncopyable {
  public:
diff --git a/src/stream.cpp b/src/stream.cpp
index f285e0a..7df635f 100644
--- a/src/stream.cpp
+++ b/src/stream.cpp
@@ -1,6 +1,6 @@
-#include "stream.h"
 #include <iostream>
-#include "exp.h"
+
+#include "stream.h"
 
 #ifndef YAML_PREFETCH_SIZE
 #define YAML_PREFETCH_SIZE 2048
diff --git a/src/tag.cpp b/src/tag.cpp
index 6e2f5b9..5143552 100644
--- a/src/tag.cpp
+++ b/src/tag.cpp
@@ -1,9 +1,10 @@
-#include "tag.h"
-#include "directives.h"
-#include "token.h"
 #include <cassert>
 #include <stdexcept>
 
+#include "directives.h"  // IWYU pragma: keep
+#include "tag.h"
+#include "token.h"
+
 namespace YAML {
 Tag::Tag(const Token& token) : type(static_cast<TYPE>(token.data)) {
   switch (type) {
diff --git a/src/tag.h b/src/tag.h
index f1768ba..ac30673 100644
--- a/src/tag.h
+++ b/src/tag.h
@@ -10,8 +10,8 @@
 #include <string>
 
 namespace YAML {
-struct Token;
 struct Directives;
+struct Token;
 
 struct Tag {
   enum TYPE {
diff --git a/test/core/parsertests.cpp b/test/core/parsertests.cpp
index fea10c3..95eb168 100644
--- a/test/core/parsertests.cpp
+++ b/test/core/parsertests.cpp
@@ -1,8 +1,15 @@
-#include "parsertests.h"
-#include "handlermacros.h"
-#include "yaml-cpp/yaml.h"
 #include <iostream>
 
+#include "handlermacros.h"
+#include "parsertests.h"  // IWYU pragma: keep
+#include "teststruct.h"
+#include "yaml-cpp/parser.h"
+
+namespace YAML {
+class Exception;
+class ParserException;
+}  // namespace YAML
+
 namespace Test {
 namespace Parser {
 TEST NoEndOfMapFlow() {
diff --git a/test/core/spectests.cpp b/test/core/spectests.cpp
index 549b19c..66692bf 100644
--- a/test/core/spectests.cpp
+++ b/test/core/spectests.cpp
@@ -1,9 +1,10 @@
-#include "spectests.h"
-#include "handlermacros.h"
-#include "specexamples.h"
-#include "yaml-cpp/yaml.h"
 #include <cassert>
 
+#include "handlermacros.h"
+#include "specexamples.h"  // IWYU pragma: keep
+#include "spectests.h"  // IWYU pragma: keep
+#include "yaml-cpp/yaml.h"  // IWYU pragma: keep
+
 namespace Test {
 namespace Spec {
 // 2.1
diff --git a/test/emittertests.cpp b/test/emittertests.cpp
index 7dbb118..1cade03 100644
--- a/test/emittertests.cpp
+++ b/test/emittertests.cpp
@@ -1,8 +1,9 @@
-#include "tests.h"
-#include "handlermacros.h"
-#include "yaml-cpp/yaml.h"
 #include <iostream>
 
+#include "teststruct.h"
+#include "yaml-cpp/eventhandler.h"
+#include "yaml-cpp/yaml.h"  // IWYU pragma: keep
+
 namespace Test {
 namespace Emitter {
 ////////////////////////////////////////////////////////////////////////////////////////////////////////
diff --git a/test/ostream_wrapper_test.cpp b/test/ostream_wrapper_test.cpp
index d325a51..cdc1f05 100644
--- a/test/ostream_wrapper_test.cpp
+++ b/test/ostream_wrapper_test.cpp
@@ -1,8 +1,8 @@
-#include "yaml-cpp/ostream_wrapper.h"
-
+#include <stddef.h>
 #include <sstream>
 
 #include "gtest/gtest.h"
+#include "yaml-cpp/ostream_wrapper.h"
 
 namespace {
 TEST(OstreamWrapperTest, BufferNoWrite) {
diff --git a/test/spectests.cpp b/test/spectests.cpp
index 92475b9..156501f 100644
--- a/test/spectests.cpp
+++ b/test/spectests.cpp
@@ -1,7 +1,12 @@
-#include "spectests.h"
-#include "yaml-cpp/yaml.h"
 #include <iostream>
 
+#include "spectests.h"
+#include "yaml-cpp/yaml.h"  // IWYU pragma: keep
+
+namespace YAML {
+class Exception;
+}  // namespace YAML
+
 namespace Test {
 namespace {
 void RunSpecTest(TEST (*test)(), const std::string& index,
diff --git a/test/tests.cpp b/test/tests.cpp
index 3c20995..f50e2fb 100644
--- a/test/tests.cpp
+++ b/test/tests.cpp
@@ -1,13 +1,13 @@
-#include "tests.h"
+#include <fstream>
+#include <iostream>
+#include <sstream>
+#include <vector>
+
 #include "emittertests.h"
 #include "nodetests.h"
 #include "parsertests.h"
 #include "spectests.h"
-#include "yaml-cpp/yaml.h"
-#include <fstream>
-#include <sstream>
-#include <vector>
-#include <iostream>
+#include "tests.h"
 
 namespace Test {
 void RunAll() {
diff --git a/util/read.cpp b/util/read.cpp
index 97514aa..4af26a9 100644
--- a/util/read.cpp
+++ b/util/read.cpp
@@ -1,7 +1,7 @@
-#include "yaml-cpp/yaml.h"
-#include "yaml-cpp/eventhandler.h"
 #include <iostream>
 
+#include "yaml-cpp/yaml.h"  // IWYU pragma: keep
+
 class NullEventHandler : public YAML::EventHandler {
  public:
   typedef YAML::Mark Mark;
diff --git a/util/sandbox.cpp b/util/sandbox.cpp
index bcac992..c5637fe 100644
--- a/util/sandbox.cpp
+++ b/util/sandbox.cpp
@@ -1,7 +1,8 @@
-#include "yaml-cpp/yaml.h"
-#include "yaml-cpp/eventhandler.h"
 #include <iostream>
 
+#include "yaml-cpp/eventhandler.h"
+#include "yaml-cpp/yaml.h"  // IWYU pragma: keep
+
 class NullEventHandler : public YAML::EventHandler {
  public:
   typedef YAML::Mark Mark;