diff --git a/lib/cbor.dart b/lib/cbor.dart
index 12b8d95..8aa94d7 100644
--- a/lib/cbor.dart
+++ b/lib/cbor.dart
@@ -78,6 +78,7 @@
 /// * [CborRegex]
 /// * [CborDateTimeFloat]
 /// * [CborDecimalFraction]
+/// * [CborRationalNumber]
 /// * [CborBigFloat]
 library cbor;
 
diff --git a/lib/src/decoder/stage3.dart b/lib/src/decoder/stage3.dart
index 2368ac2..49c1dd7 100644
--- a/lib/src/decoder/stage3.dart
+++ b/lib/src/decoder/stage3.dart
@@ -234,6 +234,26 @@ CborList _createList(
   CborLengthType type,
 ) {
   switch (raw.tags.lastWhereOrNull(isHintSubtype)) {
+    case CborTag.rationalNumber:
+      if (items.length != 2) {
+        break;
+      }
+
+      final numerator = items[0];
+      final denominator = items[1];
+
+      if (numerator is! CborInt ||
+          denominator is! CborInt ||
+          denominator.toInt() == 0) {
+        break;
+      }
+
+      return CborRationalNumber(
+        numerator: numerator,
+        denominator: denominator,
+        tags: raw.tags,
+        type: type,
+      );
     case CborTag.decimalFraction:
       if (items.length != 2) {
         break;
diff --git a/lib/src/value/list.dart b/lib/src/value/list.dart
index b1a4861..d8e7547 100644
--- a/lib/src/value/list.dart
+++ b/lib/src/value/list.dart
@@ -238,9 +238,88 @@ class _CborDecimalFractionImpl extends DelegatingList<CborValue>
   @override
   void encode(EncodeSink sink) {
     sink.addTags(tags);
-    sink.addHeaderInfo(4, const Arg.int(2));
+    sink.addHeaderInfo(
+      4,
+      switch (type) {
+        CborLengthType.definite || CborLengthType.auto => const Arg.int(2),
+        CborLengthType.indefinite => Arg.indefiniteLength,
+      },
+    );
     exponent.encode(sink);
     mantissa.encode(sink);
+
+    if (type == CborLengthType.indefinite) {
+      (const Break()).encode(sink);
+    }
+  }
+}
+
+/// A CBOR rational number (m / n).
+/// https://peteroupc.github.io/CBOR/rational.html
+abstract class CborRationalNumber extends CborList {
+  factory CborRationalNumber({
+    required CborInt numerator,
+    required CborInt denominator,
+    List<int> tags,
+    CborLengthType type,
+  }) = _CborRationalNumberImpl;
+
+  CborInt get numerator;
+
+  CborInt get denominator;
+}
+
+class _CborRationalNumberImpl extends DelegatingList<CborValue>
+    with CborValueMixin
+    implements CborRationalNumber {
+  _CborRationalNumberImpl({
+    required this.numerator,
+    required this.denominator,
+    this.tags = const [CborTag.rationalNumber],
+    this.type = CborLengthType.auto,
+  })  : assert(denominator.toInt() != 0),
+        super(List.of([numerator, denominator], growable: false));
+
+  @override
+  final CborInt numerator;
+  @override
+  final CborInt denominator;
+
+  @override
+  final List<int> tags;
+
+  @override
+  final CborLengthType type;
+
+  @override
+  Object? toObjectInternal(Set<Object> cyclicCheck, ToObjectOptions o) {
+    return [numerator.toBigInt(), denominator.toBigInt()];
+  }
+
+  @override
+  Object? toJsonInternal(Set<Object> cyclicCheck, ToJsonOptions o) {
+    return [
+      numerator.toJsonInternal(cyclicCheck, o),
+      denominator.toJsonInternal(cyclicCheck, o),
+    ];
+  }
+
+  @override
+  void encode(EncodeSink sink) {
+    sink.addTags(tags);
+    sink.addHeaderInfo(
+      4,
+      switch (type) {
+        CborLengthType.definite || CborLengthType.auto => const Arg.int(2),
+        CborLengthType.indefinite => Arg.indefiniteLength,
+      },
+    );
+    numerator.encode(sink);
+    denominator.encode(sink);
+
+    if (type == CborLengthType.indefinite) {
+      (const Break()).encode(sink);
+    }
   }
 }
 
@@ -286,9 +365,19 @@ class _CborBigFloatImpl extends DelegatingList<CborValue>
   @override
   void encode(EncodeSink sink) {
     sink.addTags(tags);
-    sink.addHeaderInfo(4, const Arg.int(2));
+    sink.addHeaderInfo(
+      4,
+      switch (type) {
+        CborLengthType.definite || CborLengthType.auto => const Arg.int(2),
+        CborLengthType.indefinite => Arg.indefiniteLength,
+      },
+    );
     exponent.encode(sink);
     mantissa.encode(sink);
+
+    if (type == CborLengthType.indefinite) {
+      (const Break()).encode(sink);
+    }
   }
 
   @override
diff --git a/lib/src/value/value.dart b/lib/src/value/value.dart
index 5d68af5..35db8e5 100644
--- a/lib/src/value/value.dart
+++ b/lib/src/value/value.dart
@@ -36,6 +36,7 @@ class CborTag {
   static const int expectedConversionToBase64 = 22;
   static const int expectedConversionToBase64Url = 21;
   static const int expectedConversionToBase16 = 23;
+  static const int rationalNumber = 30;
   static const int uri = 32;
   static const int base64Url = 33;
   static const int base64 = 34;
diff --git a/test/rational_number_test.dart b/test/rational_number_test.dart
new file mode 100644
index 0000000..c7efed7
--- /dev/null
+++ b/test/rational_number_test.dart
@@ -0,0 +1,103 @@
+/*
+ * Package : Cbor
+ * Author : Alex Dochioiu <alex@vespr.xyz>
+ * Date   : 19/06/2024
+ * Copyright :  Alex Dochioiu
+ */
+
+import 'package:cbor/cbor.dart';
+import 'package:test/test.dart';
+
+void main() {
+  group(
+      "RationalNumber",
+      () => {
+            group('encoding tests', () {
+              test('encode auto length', () {
+                expect(
+                  cbor.encode(
+                    CborRationalNumber(
+                      numerator: CborInt(BigInt.from(1)),
+                      denominator: CborSmallInt(2),
+                      type: CborLengthType.auto,
+                    ),
+                  ),
+                  [0xd8, 0x1e, 0x82, 0x1, 0x2],
+                );
+              });
+
+              test('encode definite length', () {
+                expect(
+                  cbor.encode(
+                    CborRationalNumber(
+                      numerator: CborInt(BigInt.from(1)),
+                      denominator: CborSmallInt(2),
+                      type: CborLengthType.definite,
+                    ),
+                  ),
+                  [0xd8, 0x1e, 0x82, 0x1, 0x2],
+                );
+              });
+
+              test('encode indefinite length', () {
+                expect(
+                  cbor.encode(
+                    CborRationalNumber(
+                      numerator: CborInt(BigInt.from(1)),
+                      denominator: CborSmallInt(2),
+                      type: CborLengthType.indefinite,
+                    ),
+                  ),
+                  [0xd8, 0x1e, 0x9f, 0x1, 0x2, 0xff],
+                );
+              });
+            }),
+            group('decoding tests', () {
+              test('auto length', () {
+                expect(
+                  cbor.decode([0xd8, 0x1e, 0x82, 0x1, 0x2]),
+                  CborRationalNumber(
+                    numerator: CborInt(BigInt.from(1)),
+                    denominator: CborSmallInt(2),
+                    type: CborLengthType.auto,
+                  ),
+                );
+              });
+
+              test('definite length', () {
+                expect(
+                  cbor.decode([0xd8, 0x1e, 0x82, 0x1, 0x2]),
+                  CborRationalNumber(
+                    numerator: CborInt(BigInt.from(1)),
+                    denominator: CborSmallInt(2),
+                    type: CborLengthType.definite,
+                  ),
+                );
+              });
+
+              test('indefinite length', () {
+                expect(
+                  cbor.decode([0xd8, 0x1e, 0x9f, 0x1, 0x2, 0xff]),
+                  CborRationalNumber(
+                    numerator: CborInt(BigInt.from(1)),
+                    denominator: CborSmallInt(2),
+                    type: CborLengthType.indefinite,
+                  ),
+                );
+              });
+
+              test('not CborRationalNumber when denominator is 0', () {
+                expect(
+                  cbor.decode([0xd8, 0x1e, 0x9f, 0x1, 0x0, 0xff])
+                      is CborRationalNumber,
+                  false,
+                );
+
+                expect(
+                  cbor.decode([0xd8, 0x1e, 0x9f, 0x1, 0x0, 0xff]) is CborList,
+                  true,
+                );
+              });
+            }),
+          });
+}