diff --git a/java-frontend/src/main/java/org/sonar/java/model/JParser.java b/java-frontend/src/main/java/org/sonar/java/model/JParser.java
index 777d928b86..1cf6f17618 100644
--- a/java-frontend/src/main/java/org/sonar/java/model/JParser.java
+++ b/java-frontend/src/main/java/org/sonar/java/model/JParser.java
@@ -2620,15 +2620,23 @@ private JavaTree.AnnotatedTypeTree convertSimpleType(SimpleType e) {
 
   private JavaTree.UnionTypeTreeImpl convertUnionType(UnionType e) {
     QualifiedIdentifierListTreeImpl alternatives = QualifiedIdentifierListTreeImpl.emptyList();
+    ITypeBinding[] alternativeBindings = new ITypeBinding[e.types().size()];
     for (int i = 0; i < e.types().size(); i++) {
       Type o = (Type) e.types().get(i);
-      alternatives.add(convertType(o));
+      TypeTree typeTree = convertType(o);
+      alternatives.add(typeTree);
+      if (typeTree instanceof AbstractTypedTree typedTree && typedTree.typeBinding != null) {
+        alternativeBindings[i] = typedTree.typeBinding;
+      } else {
+        alternativeBindings[i] = o.resolveBinding();
+      }
       if (i < e.types().size() - 1) {
         alternatives.separators().add(firstTokenAfter(o, TerminalToken.TokenNameOR));
       }
     }
     JavaTree.UnionTypeTreeImpl t = new JavaTree.UnionTypeTreeImpl(alternatives);
     t.typeBinding = e.resolveBinding();
+    t.alternativeBindings = alternativeBindings;
     return t;
   }
 
diff --git a/java-frontend/src/main/java/org/sonar/java/model/JSema.java b/java-frontend/src/main/java/org/sonar/java/model/JSema.java
index 6a2f1ffd52..5a7e7d4d1a 100644
--- a/java-frontend/src/main/java/org/sonar/java/model/JSema.java
+++ b/java-frontend/src/main/java/org/sonar/java/model/JSema.java
@@ -50,6 +50,7 @@ public final class JSema implements Sema {
   private final Map<Symbol.TypeSymbol, JInitializerBlockSymbol> staticInitializerBlockSymbols = new HashMap<>();
   private final Map<IAnnotationBinding, JSymbolMetadata.JAnnotationInstance> annotations = new HashMap<>();
   private final Map<String, Type> nameToTypeCache = new HashMap<>();
+  final Map<ITypeBinding, ITypeBinding[]> unionTypeAlternatives = new HashMap<>();
 
   JSema(AST ast) {
     this.ast = ast;
diff --git a/java-frontend/src/main/java/org/sonar/java/model/JType.java b/java-frontend/src/main/java/org/sonar/java/model/JType.java
index 18e8cf72ab..0f0a15c858 100644
--- a/java-frontend/src/main/java/org/sonar/java/model/JType.java
+++ b/java-frontend/src/main/java/org/sonar/java/model/JType.java
@@ -210,34 +210,57 @@ public String fullyQualifiedName() {
     return fullyQualifiedName;
   }
 
-  private static String fullyQualifiedName(ITypeBinding typeBinding) {
-    String qualifiedName;
+  private String fullyQualifiedName(ITypeBinding typeBinding) {
+    String qualifiedName = baseQualifiedName(typeBinding);
+
+    if (typeBinding.isIntersectionType()) {
+      return buildIntersectionTypeName(typeBinding, qualifiedName);
+    } else if (isUnionType()) {
+      return buildUnionTypeName(typeBinding, qualifiedName);
+    }
+    return qualifiedName;
+  }
+
+  private String baseQualifiedName(ITypeBinding typeBinding) {
     if (typeBinding.isNullType()) {
-      qualifiedName = "<nulltype>";
+      return "<nulltype>";
     } else if (typeBinding.isPrimitive()) {
-      qualifiedName = typeBinding.getName();
+      return typeBinding.getName();
     } else if (typeBinding.isArray()) {
-      qualifiedName = fullyQualifiedName(typeBinding.getComponentType()) + "[]";
+      return fullyQualifiedName(typeBinding.getComponentType()) + "[]";
     } else if (typeBinding.isCapture()) {
-      qualifiedName = "!capture!";
+      return "!capture!";
     } else if (typeBinding.isTypeVariable()) {
-      qualifiedName = typeBinding.getName();
+      return typeBinding.getName();
     } else {
-      qualifiedName = typeBinding.getBinaryName();
-      if (qualifiedName == null) {
+      String binaryName = typeBinding.getBinaryName();
+      if (binaryName == null) {
         // e.g. anonymous class in unreachable code
-        qualifiedName = typeBinding.getKey();
+        return typeBinding.getKey();
       }
+      return binaryName;
     }
-    if (typeBinding.isIntersectionType()) {
-      TreeSet<String> intersectionTypes = new TreeSet<>();
-      intersectionTypes.add(qualifiedName);
-      for (ITypeBinding typeBound : typeBinding.getTypeBounds()) {
-        intersectionTypes.add(fullyQualifiedName(typeBound));
-      }
-      qualifiedName = String.join(" & ", intersectionTypes);
+  }
+
+  private String buildIntersectionTypeName(ITypeBinding typeBinding, String baseName) {
+    TreeSet<String> intersectionTypes = new TreeSet<>();
+    intersectionTypes.add(baseName);
+    for (ITypeBinding typeBound : typeBinding.getTypeBounds()) {
+      intersectionTypes.add(fullyQualifiedName(typeBound));
     }
-    return qualifiedName;
+    return String.join(" & ", intersectionTypes);
+  }
+
+  private String buildUnionTypeName(ITypeBinding typeBinding, String baseName) {
+    ITypeBinding[] alternatives = sema.unionTypeAlternatives.get(typeBinding);
+    if (alternatives == null) {
+      return baseName;
+    }
+    TreeSet<String> unionTypes = new TreeSet<>();
+    for (ITypeBinding alternative : alternatives) {
+      unionTypes.add(fullyQualifiedName(alternative));
+    }
+    return String.join(" | ", unionTypes);
   }
 
   @Override
@@ -258,6 +281,24 @@ public Type[] getIntersectionTypes() {
     return types;
   }
 
+  @Override
+  public boolean isUnionType() {
+    return sema.unionTypeAlternatives.containsKey(typeBinding);
+  }
+
+  @Override
+  public Type[] getUnionTypes() {
+    ITypeBinding[] alternatives = sema.unionTypeAlternatives.get(typeBinding);
+    if (alternatives == null) {
+      return new Type[] { this };
+    }
+    Type[] types = new Type[alternatives.length];
+    for (int i = 0; i < alternatives.length; i++) {
+      types[i] = sema.type(alternatives[i]);
+    }
+    return types;
+  }
+
   /**
    * @see JSymbol#name()
    */
diff --git a/java-frontend/src/main/java/org/sonar/java/model/JavaTree.java b/java-frontend/src/main/java/org/sonar/java/model/JavaTree.java
index 895bc18860..95d2cf83c5 100644
--- a/java-frontend/src/main/java/org/sonar/java/model/JavaTree.java
+++ b/java-frontend/src/main/java/org/sonar/java/model/JavaTree.java
@@ -38,6 +38,7 @@
 import org.sonar.java.model.expression.AssessableExpressionTree;
 import org.sonar.java.model.expression.TypeArgumentListTreeImpl;
 import org.sonar.plugins.java.api.semantic.Symbol;
+import org.sonar.plugins.java.api.semantic.Type;
 import org.sonar.plugins.java.api.tree.AnnotationTree;
 import org.sonar.plugins.java.api.tree.ArrayTypeTree;
 import org.sonar.plugins.java.api.tree.CompilationUnitTree;
@@ -476,6 +477,7 @@ public List<Tree> children() {
 
   public static class UnionTypeTreeImpl extends AbstractTypedTree implements UnionTypeTree {
     private final ListTree<TypeTree> typeAlternatives;
+    ITypeBinding[] alternativeBindings;
 
     public UnionTypeTreeImpl(QualifiedIdentifierListTreeImpl typeAlternatives) {
       this.typeAlternatives = Objects.requireNonNull(typeAlternatives);
@@ -505,6 +507,14 @@ public List<Tree> children() {
     public List<AnnotationTree> annotations() {
       return Collections.emptyList();
     }
+
+    @Override
+    public Type symbolType() {
+      if (typeBinding != null && alternativeBindings != null) {
+        root.sema.unionTypeAlternatives.put(typeBinding, alternativeBindings);
+      }
+      return super.symbolType();
+    }
   }
 
   public static class NotImplementedTreeImpl extends AssessableExpressionTree {
diff --git a/java-frontend/src/main/java/org/sonar/java/model/Symbols.java b/java-frontend/src/main/java/org/sonar/java/model/Symbols.java
index 7c89cf26b5..f65373a6d2 100644
--- a/java-frontend/src/main/java/org/sonar/java/model/Symbols.java
+++ b/java-frontend/src/main/java/org/sonar/java/model/Symbols.java
@@ -469,5 +469,15 @@ public boolean isIntersectionType() {
     public Type[] getIntersectionTypes() {
       return new Type[] { this };
     }
+
+    @Override
+    public boolean isUnionType() {
+      return false;
+    }
+
+    @Override
+    public Type[] getUnionTypes() {
+      return new Type[] { this };
+    }
   }
 }
diff --git a/java-frontend/src/main/java/org/sonar/plugins/java/api/semantic/Type.java b/java-frontend/src/main/java/org/sonar/plugins/java/api/semantic/Type.java
index 014200e911..23bbc214ff 100644
--- a/java-frontend/src/main/java/org/sonar/plugins/java/api/semantic/Type.java
+++ b/java-frontend/src/main/java/org/sonar/plugins/java/api/semantic/Type.java
@@ -299,4 +299,21 @@ interface ArrayType extends Type {
    */
   Type[] getIntersectionTypes();
 
+  /**
+   * Check if this type is a union type. For example, return true for the type of 'e' in the following code:
+   * <code><pre>
+   *   try { } catch (IOException | SQLException e) { }
+   *</pre></code>
+   */
+  boolean isUnionType();
+
+  /**
+   * This method returns more than one type when {@link #isUnionType()} is true. For example, it
+   * returns {@code ["java.io.IOException", "java.sql.SQLException"] } for the type of 'e' in the following code:
+   * <code><pre>
+   *   try { } catch (IOException | SQLException e) { }
+   *</pre></code>
+   */
+  Type[] getUnionTypes();
+
 }
diff --git a/java-frontend/src/test/java/org/sonar/java/model/JParserSemanticTest.java b/java-frontend/src/test/java/org/sonar/java/model/JParserSemanticTest.java
index 3ef832296b..e367f66f6e 100644
--- a/java-frontend/src/test/java/org/sonar/java/model/JParserSemanticTest.java
+++ b/java-frontend/src/test/java/org/sonar/java/model/JParserSemanticTest.java
@@ -1497,11 +1497,69 @@ void type_union() {
     Type symbolType = t.symbolType();
     assertThat(symbolType).isNotNull();
     assertThat(symbolType.isUnknown()).isFalse();
-    // "fullyQualifiedName()" should be unique for each different type, like for example "java.lang.MatchException | java.lang.NumberFormatException"
-    // this will be fixed by SONARJAVA-5718
-    assertThat(symbolType.fullyQualifiedName()).isEqualTo("java.lang.RuntimeException");
-    assertThat(symbolType.getIntersectionTypes()).extracting(Type::fullyQualifiedName)
-      .containsExactly("java.lang.RuntimeException");
+    // "fullyQualifiedName()" should be unique for each different type
+    assertThat(symbolType.fullyQualifiedName()).isEqualTo("java.lang.MatchException | java.lang.NumberFormatException");
+    assertThat(symbolType.isUnionType()).isTrue();
+    assertThat(symbolType.getUnionTypes()).extracting(Type::fullyQualifiedName)
+      .containsExactly("java.lang.MatchException", "java.lang.NumberFormatException");
+  }
+
+  @Test
+  void type_union_with_three_alternatives() {
+    CompilationUnitTree cu = test("class C { void m() { try { } catch (MatchException | NumberFormatException | ArithmeticException v) { } } }");
+    ClassTree c = (ClassTree) cu.types().get(0);
+    MethodTree m = (MethodTree) c.members().get(0);
+    TryStatementTree s = (TryStatementTree) m.block().body().get(0);
+    VariableTreeImpl v = (VariableTreeImpl) s.catches().get(0).parameter();
+    AbstractTypedTree t = (AbstractTypedTree) v.type();
+    Type symbolType = t.symbolType();
+    assertThat(symbolType.isUnionType()).isTrue();
+    // FQN should be sorted alphabetically
+    assertThat(symbolType.fullyQualifiedName()).isEqualTo("java.lang.ArithmeticException | java.lang.MatchException | java.lang.NumberFormatException");
+    assertThat(symbolType.getUnionTypes()).hasSize(3);
+    // getUnionTypes() returns types in source order, not sorted
+    assertThat(symbolType.getUnionTypes()).extracting(Type::fullyQualifiedName)
+      .containsExactly("java.lang.MatchException", "java.lang.NumberFormatException", "java.lang.ArithmeticException");
+  }
+
+  @Test
+  void type_union_ordering() {
+    // Test that union types are sorted alphabetically in FQN
+    CompilationUnitTree cu = test("class C { void m() { try { } catch (NumberFormatException | MatchException v) { } } }");
+    ClassTree c = (ClassTree) cu.types().get(0);
+    MethodTree m = (MethodTree) c.members().get(0);
+    TryStatementTree s = (TryStatementTree) m.block().body().get(0);
+    VariableTreeImpl v = (VariableTreeImpl) s.catches().get(0).parameter();
+    AbstractTypedTree t = (AbstractTypedTree) v.type();
+    Type symbolType = t.symbolType();
+    // Should be sorted: MatchException comes before NumberFormatException
+    assertThat(symbolType.fullyQualifiedName()).isEqualTo("java.lang.MatchException | java.lang.NumberFormatException");
+  }
+
+  @Test
+  void non_union_type_returns_false_for_isUnionType() {
+    CompilationUnitTree cu = test("class C { void m() { try { } catch (NumberFormatException v) { } } }");
+    ClassTree c = (ClassTree) cu.types().get(0);
+    MethodTree m = (MethodTree) c.members().get(0);
+    TryStatementTree s = (TryStatementTree) m.block().body().get(0);
+    VariableTreeImpl v = (VariableTreeImpl) s.catches().get(0).parameter();
+    AbstractTypedTree t = (AbstractTypedTree) v.type();
+    Type symbolType = t.symbolType();
+    assertThat(symbolType.isUnionType()).isFalse();
+    assertThat(symbolType.getUnionTypes()).hasSize(1);
+    assertThat(symbolType.getUnionTypes()[0]).isEqualTo(symbolType);
+  }
+
+  @Test
+  void primitive_type_is_not_union() {
+    CompilationUnitTree cu = test("class C { void m(int x) { } }");
+    ClassTree c = (ClassTree) cu.types().get(0);
+    MethodTree m = (MethodTree) c.members().get(0);
+    VariableTreeImpl v = (VariableTreeImpl) m.parameters().get(0);
+    Type symbolType = v.symbol().type();
+    assertThat(symbolType.isUnionType()).isFalse();
+    assertThat(symbolType.getUnionTypes()).hasSize(1);
+    assertThat(symbolType.getUnionTypes()[0]).isEqualTo(symbolType);
   }
 
   @Test