diff --git a/autotests/syntaxrepository_test.cpp b/autotests/syntaxrepository_test.cpp
--- a/autotests/syntaxrepository_test.cpp
+++ b/autotests/syntaxrepository_test.cpp
@@ -148,6 +148,27 @@
         QCOMPARE(def.foldingIgnoreList(), QStringList() << QLatin1String("(?:\\s+|\\s*#.*)"));
     }
 
+    void testIncludedDefinitions()
+    {
+        auto def = m_repo.definitionForName(QLatin1String("C++"));
+        QVERIFY(def.isValid());
+        auto defs = def.includedDefinitions();
+
+        const QStringList expectedDefinitionNames = {
+            QStringLiteral("C++"),
+            QStringLiteral("ISO C++"),
+            QStringLiteral("GCCExtensions"),
+            QStringLiteral("Doxygen"),
+            QStringLiteral("Alerts"),
+            QStringLiteral("Modelines")
+        };
+        QStringList definitionNames;
+        for (auto d : defs) {
+            definitionNames.push_back(d.name());
+        }
+        QCOMPARE(definitionNames, expectedDefinitionNames);
+    }
+
     void testReload()
     {
         auto def = m_repo.definitionForName(QLatin1String("QML"));
diff --git a/src/lib/definition.h b/src/lib/definition.h
--- a/src/lib/definition.h
+++ b/src/lib/definition.h
@@ -172,6 +172,15 @@
      */
     QStringList foldingIgnoreList() const;
 
+    /**
+     * Returns a list of Definitions that are referenced with the IncludeRules rule.
+     * The returned list includes this Definition as well as any recursively used
+     * Definition.
+     *
+     * @since 5.49
+     */
+    QVector<Definition> includedDefinitions() const;
+
 private:
     friend class DefinitionData;
     friend class DefinitionRef;
diff --git a/src/lib/definition.cpp b/src/lib/definition.cpp
--- a/src/lib/definition.cpp
+++ b/src/lib/definition.cpp
@@ -34,6 +34,7 @@
 #include <QFile>
 #include <QHash>
 #include <QJsonObject>
+#include <QQueue>
 #include <QStringList>
 #include <QVector>
 #include <QXmlStreamReader>
@@ -186,6 +187,33 @@
     return d->foldingIgnoreList;
 }
 
+QVector<Definition> Definition::includedDefinitions() const
+{
+    d->load();
+
+    QVector<Definition> definitions;
+
+    QQueue<Definition> queue;
+    queue.enqueue(*this);
+    while (!queue.isEmpty()) {
+        const auto definition = queue.dequeue();
+        definitions.push_back(definition);
+
+        // Iterate all context rules to find associated Definitions. This will
+        // automatically catch other Definitions referenced with IncludeRuldes.
+        foreach (const auto & context, definition.d->contexts) {
+            foreach (const auto &rule, context->rules()) {
+                if ((!definitions.contains(rule->definition())) &&
+                    (!queue.contains(rule->definition())))
+                {
+                    queue.enqueue(rule->definition());
+                }
+            }
+        }
+    }
+    return definitions;
+}
+
 Context* DefinitionData::initialContext() const
 {
     Q_ASSERT(!contexts.isEmpty());