diff --git a/src/libs/3rdparty/syntax-highlighting/src/lib/abstracthighlighter_p.h b/src/libs/3rdparty/syntax-highlighting/src/lib/abstracthighlighter_p.h
index c36932c29df..f1492df786b 100644
--- a/src/libs/3rdparty/syntax-highlighting/src/lib/abstracthighlighter_p.h
+++ b/src/libs/3rdparty/syntax-highlighting/src/lib/abstracthighlighter_p.h
@@ -27,10 +27,6 @@
 #include "definition.h"
 #include "theme.h"
 
-QT_BEGIN_NAMESPACE
-class QStringList;
-QT_END_NAMESPACE
-
 namespace KSyntaxHighlighting
 {
 class ContextSwitch;
diff --git a/src/libs/3rdparty/syntax-highlighting/src/lib/definition.h b/src/libs/3rdparty/syntax-highlighting/src/lib/definition.h
index e17dfb97a4d..3219bf03b9e 100644
--- a/src/libs/3rdparty/syntax-highlighting/src/lib/definition.h
+++ b/src/libs/3rdparty/syntax-highlighting/src/lib/definition.h
@@ -33,7 +33,6 @@
 QT_BEGIN_NAMESPACE
 class QChar;
 class QString;
-class QStringList;
 QT_END_NAMESPACE
 
 namespace KSyntaxHighlighting
diff --git a/src/libs/3rdparty/syntax-highlighting/src/lib/state_p.h b/src/libs/3rdparty/syntax-highlighting/src/lib/state_p.h
index fbc16861439..1156ce981a0 100644
--- a/src/libs/3rdparty/syntax-highlighting/src/lib/state_p.h
+++ b/src/libs/3rdparty/syntax-highlighting/src/lib/state_p.h
@@ -30,10 +30,6 @@
 
 #include "definitionref_p.h"
 
-QT_BEGIN_NAMESPACE
-class QStringList;
-QT_END_NAMESPACE
-
 namespace KSyntaxHighlighting
 {
 class Context;
diff --git a/src/libs/extensionsystem/pluginspec.h b/src/libs/extensionsystem/pluginspec.h
index 4ad702b2163..d8d85ba5201 100644
--- a/src/libs/extensionsystem/pluginspec.h
+++ b/src/libs/extensionsystem/pluginspec.h
@@ -32,7 +32,6 @@
 #include <QVector>
 
 QT_BEGIN_NAMESPACE
-class QStringList;
 class QRegularExpression;
 QT_END_NAMESPACE
 
diff --git a/src/libs/qmljs/persistenttrie.h b/src/libs/qmljs/persistenttrie.h
index 184525b13e8..19d7c3a0e79 100644
--- a/src/libs/qmljs/persistenttrie.h
+++ b/src/libs/qmljs/persistenttrie.h
@@ -34,7 +34,6 @@
 #include <utility>
 
 QT_FORWARD_DECLARE_CLASS(QString)
-QT_FORWARD_DECLARE_CLASS(QStringList)
 QT_FORWARD_DECLARE_CLASS(QDebug)
 
 namespace QmlJS {
diff --git a/src/libs/utils/codegeneration.h b/src/libs/utils/codegeneration.h
index 2738d7b27aa..06d0ca258d8 100644
--- a/src/libs/utils/codegeneration.h
+++ b/src/libs/utils/codegeneration.h
@@ -27,9 +27,10 @@
 
 #include "utils_global.h"
 
+#include <QStringList>
+
 QT_BEGIN_NAMESPACE
 class QTextStream;
-class QStringList;
 QT_END_NAMESPACE
 
 namespace Utils {
diff --git a/src/libs/utils/mimetypes/mimetype.h b/src/libs/utils/mimetypes/mimetype.h
index b4ac5b4c39d..4d64de32754 100644
--- a/src/libs/utils/mimetypes/mimetype.h
+++ b/src/libs/utils/mimetypes/mimetype.h
@@ -46,7 +46,6 @@
 
 QT_BEGIN_NAMESPACE
 class QFileinfo;
-class QStringList;
 QT_END_NAMESPACE
 
 namespace Utils {
diff --git a/src/libs/utils/shellcommand.h b/src/libs/utils/shellcommand.h
index a54e8fb4014..df89abad6e6 100644
--- a/src/libs/utils/shellcommand.h
+++ b/src/libs/utils/shellcommand.h
@@ -35,7 +35,6 @@
 
 QT_BEGIN_NAMESPACE
 class QMutex;
-class QStringList;
 class QVariant;
 class QProcessEnvironment;
 template <typename T>
diff --git a/src/libs/utils/textfileformat.h b/src/libs/utils/textfileformat.h
index 9ac452a6e5a..f95d1e7913f 100644
--- a/src/libs/utils/textfileformat.h
+++ b/src/libs/utils/textfileformat.h
@@ -27,10 +27,10 @@
 
 #include "utils_global.h"
 
+#include <QStringList>
+
 QT_BEGIN_NAMESPACE
 class QTextCodec;
-class QStringList;
-class QString;
 class QByteArray;
 QT_END_NAMESPACE
 
diff --git a/src/plugins/clangpchmanager/projectupdater.h b/src/plugins/clangpchmanager/projectupdater.h
index 16d662004fb..0b3865d7b41 100644
--- a/src/plugins/clangpchmanager/projectupdater.h
+++ b/src/plugins/clangpchmanager/projectupdater.h
@@ -55,8 +55,6 @@ namespace ClangBackEnd {
 class ProjectManagementServerInterface;
 }
 
-QT_FORWARD_DECLARE_CLASS(QStringList)
-
 #include <vector>
 
 namespace ClangPchManager {
diff --git a/src/plugins/coreplugin/diffservice.h b/src/plugins/coreplugin/diffservice.h
index 1c241364dc4..d397c1e00a5 100644
--- a/src/plugins/coreplugin/diffservice.h
+++ b/src/plugins/coreplugin/diffservice.h
@@ -29,8 +29,6 @@
 
 #include <QObject>
 
-QT_FORWARD_DECLARE_CLASS(QStringList)
-
 namespace Core {
 
 class CORE_EXPORT DiffService
diff --git a/src/plugins/coreplugin/documentmanager.h b/src/plugins/coreplugin/documentmanager.h
index e9b9d66adb9..f05c7d0f10f 100644
--- a/src/plugins/coreplugin/documentmanager.h
+++ b/src/plugins/coreplugin/documentmanager.h
@@ -32,10 +32,6 @@
 #include <QObject>
 #include <QPair>
 
-QT_BEGIN_NAMESPACE
-class QStringList;
-QT_END_NAMESPACE
-
 namespace Utils { class FilePath; }
 
 namespace Core {
diff --git a/src/plugins/coreplugin/helpmanager.h b/src/plugins/coreplugin/helpmanager.h
index ac948b633d9..6a02e405a9e 100644
--- a/src/plugins/coreplugin/helpmanager.h
+++ b/src/plugins/coreplugin/helpmanager.h
@@ -31,7 +31,6 @@
 #include <QMap>
 
 QT_BEGIN_NAMESPACE
-class QStringList;
 class QUrl;
 QT_END_NAMESPACE
 
diff --git a/src/plugins/cpptools/includeutils.h b/src/plugins/cpptools/includeutils.h
index 310bb251c8a..59ff8b81a7a 100644
--- a/src/plugins/cpptools/includeutils.h
+++ b/src/plugins/cpptools/includeutils.h
@@ -33,7 +33,6 @@
 #include <QList>
 #include <QString>
 
-QT_FORWARD_DECLARE_CLASS(QStringList)
 QT_FORWARD_DECLARE_CLASS(QTextDocument)
 
 namespace CppTools {
diff --git a/src/plugins/cpptools/typehierarchybuilder.h b/src/plugins/cpptools/typehierarchybuilder.h
index fc1a6285150..4f623d2fdb8 100644
--- a/src/plugins/cpptools/typehierarchybuilder.h
+++ b/src/plugins/cpptools/typehierarchybuilder.h
@@ -33,8 +33,6 @@
 #include <QList>
 #include <QSet>
 
-QT_FORWARD_DECLARE_CLASS(QStringList)
-
 namespace CppTools {
 
 class CPPTOOLS_EXPORT TypeHierarchy
diff --git a/src/plugins/debugger/shared/peutils.h b/src/plugins/debugger/shared/peutils.h
index 0d25d8ace15..a50136fe4ac 100644
--- a/src/plugins/debugger/shared/peutils.h
+++ b/src/plugins/debugger/shared/peutils.h
@@ -25,12 +25,7 @@
 
 #pragma once
 
-#include <qnamespace.h>
-
-QT_BEGIN_NAMESPACE
-class QStringList;
-class QString;
-QT_END_NAMESPACE
+#include <QStringList>
 
 /* Helper functions to extract information from PE Win32 executable
  * files (cf dumpbin utility). */
diff --git a/src/plugins/designer/codemodelhelpers.h b/src/plugins/designer/codemodelhelpers.h
index 9e3e845d748..a0596e0cb9c 100644
--- a/src/plugins/designer/codemodelhelpers.h
+++ b/src/plugins/designer/codemodelhelpers.h
@@ -25,12 +25,7 @@
 
 #pragma once
 
-#include <QtGlobal>
-
-QT_BEGIN_NAMESPACE
-class QString;
-class QStringList;
-QT_END_NAMESPACE
+#include <QStringList>
 
 namespace Designer {
 namespace Internal {
diff --git a/src/plugins/designer/cpp/newclasswidget.h b/src/plugins/designer/cpp/newclasswidget.h
index 91868c13cfc..112c2cefb29 100644
--- a/src/plugins/designer/cpp/newclasswidget.h
+++ b/src/plugins/designer/cpp/newclasswidget.h
@@ -27,10 +27,6 @@
 
 #include <QWidget>
 
-QT_BEGIN_NAMESPACE
-class QStringList;
-QT_END_NAMESPACE
-
 namespace Designer {
 namespace Internal {
 
diff --git a/src/plugins/qtsupport/gettingstartedwelcomepage.h b/src/plugins/qtsupport/gettingstartedwelcomepage.h
index 213292dc752..db2bab24075 100644
--- a/src/plugins/qtsupport/gettingstartedwelcomepage.h
+++ b/src/plugins/qtsupport/gettingstartedwelcomepage.h
@@ -29,7 +29,6 @@
 
 QT_BEGIN_NAMESPACE
 class QFileInfo;
-class QStringList;
 QT_END_NAMESPACE
 
 namespace QtSupport {
diff --git a/src/plugins/valgrind/callgrind/callgrindparsedata.h b/src/plugins/valgrind/callgrind/callgrindparsedata.h
index 00fb9b79118..02fbc29e493 100644
--- a/src/plugins/valgrind/callgrind/callgrindparsedata.h
+++ b/src/plugins/valgrind/callgrind/callgrindparsedata.h
@@ -29,7 +29,6 @@
 
 QT_BEGIN_NAMESPACE
 class QString;
-class QStringList;
 QT_END_NAMESPACE
 
 namespace Valgrind {
diff --git a/src/plugins/vcsbase/vcsbaseeditorconfig.h b/src/plugins/vcsbase/vcsbaseeditorconfig.h
index 9a8f4d493f0..8f1ebaee193 100644
--- a/src/plugins/vcsbase/vcsbaseeditorconfig.h
+++ b/src/plugins/vcsbase/vcsbaseeditorconfig.h
@@ -33,7 +33,6 @@
 QT_BEGIN_NAMESPACE
 class QComboBox;
 class QToolButton;
-class QStringList;
 QT_END_NAMESPACE
 
 namespace VcsBase {