diff --git a/README.md b/README.md
index cdf896c..76ec29f 100644
--- a/README.md
+++ b/README.md
@@ -128,6 +128,21 @@ $instant->toIso8601();     # 2026-02-17T16:30:00+00:00
 $instant->toUnixSeconds(); # 1771345800
 ```
 
+The offset accepts the ISO 8601 zulu designator (`Z`) as an alias for `+00:00`, with or without fractional seconds.
+
+```php
+<?php
+
+declare(strict_types=1);
+
+use TinyBlocks\Time\Instant;
+
+$instant = Instant::fromString(value: '2026-02-17T10:30:00Z');
+
+$instant->toIso8601();     # 2026-02-17T10:30:00+00:00
+$instant->toUnixSeconds(); # 1771324200
+```
+
 #### Creating from a database timestamp
 
 Parses a database date-time string as UTC, with or without microsecond precision (e.g. MySQL `DATETIME`
diff --git a/src/Internal/Decoders/OffsetDateTimeDecoder.php b/src/Internal/Decoders/OffsetDateTimeDecoder.php
index d148ad1..9554e0a 100644
--- a/src/Internal/Decoders/OffsetDateTimeDecoder.php
+++ b/src/Internal/Decoders/OffsetDateTimeDecoder.php
@@ -11,8 +11,8 @@
 {
     private const string FORMAT = 'Y-m-d\TH:i:sP';
     private const string FORMAT_MICRO = 'Y-m-d\TH:i:s.uP';
-    private const string PATTERN = '/^\d{4}-\d{2}-\d{2}T\d{2}:\d{2}:\d{2}[+\-]\d{2}:\d{2}$/';
-    private const string PATTERN_MICRO = '/^\d{4}-\d{2}-\d{2}T\d{2}:\d{2}:\d{2}\.\d+[+\-]\d{2}:\d{2}$/';
+    private const string PATTERN = '/^\d{4}-\d{2}-\d{2}T\d{2}:\d{2}:\d{2}(?:Z|[+\-]\d{2}:\d{2})$/';
+    private const string PATTERN_MICRO = '/^\d{4}-\d{2}-\d{2}T\d{2}:\d{2}:\d{2}\.\d+(?:Z|[+\-]\d{2}:\d{2})$/';
 
     public function decode(string $value): ?DateTimeImmutable
     {
diff --git a/tests/Unit/InstantTest.php b/tests/Unit/InstantTest.php
index c469447..54fa394 100644
--- a/tests/Unit/InstantTest.php
+++ b/tests/Unit/InstantTest.php
@@ -1226,6 +1226,26 @@ public static function validStringsDataProvider(): array
                 'value'               => '2026-02-17T16:00:00.500000+05:30',
                 'expectedIso8601'     => '2026-02-17T10:30:00+00:00',
                 'expectedUnixSeconds' => 1771324200
+            ],
+            'Zulu designator'                   => [
+                'value'               => '2026-02-17T10:30:00Z',
+                'expectedIso8601'     => '2026-02-17T10:30:00+00:00',
+                'expectedUnixSeconds' => 1771324200
+            ],
+            'Zulu designator at midnight'       => [
+                'value'               => '2026-01-01T00:00:00Z',
+                'expectedIso8601'     => '2026-01-01T00:00:00+00:00',
+                'expectedUnixSeconds' => 1767225600
+            ],
+            'Zulu with microseconds'            => [
+                'value'               => '2026-02-17T10:30:00.123456Z',
+                'expectedIso8601'     => '2026-02-17T10:30:00+00:00',
+                'expectedUnixSeconds' => 1771324200
+            ],
+            'Zulu with short fraction'          => [
+                'value'               => '2026-02-17T10:30:00.272Z',
+                'expectedIso8601'     => '2026-02-17T10:30:00+00:00',
+                'expectedUnixSeconds' => 1771324200
             ]
         ];
     }
@@ -1243,7 +1263,7 @@ public static function invalidStringsDataProvider(): array
             'Truncated offset'                       => ['value' => '2026-02-17T10:30:00+00'],
             'Slash-separated date'                   => ['value' => '2026/02/17T10:30:00+00:00'],
             'Missing time separator'                 => ['value' => '2026-02-17 10:30:00+00:00'],
-            'Z suffix instead offset'                => ['value' => '2026-02-17T10:30:00Z'],
+            'Lowercase zulu designator'              => ['value' => '2026-02-17T10:30:00z'],
             'Unix timestamp as string'               => ['value' => '1771324200'],
             'Database format with invalid day'       => ['value' => '2026-02-30 08:27:21.106011'],
             'Database format with T separator'       => ['value' => '2026-02-17T08:27:21.106011'],