diff --git a/src/Assert/Assert.php b/src/Assert/Assert.php
index b1f8d627..ecc85c8a 100644
--- a/src/Assert/Assert.php
+++ b/src/Assert/Assert.php
@@ -45,6 +45,7 @@
  * @method static void validString(mixed $value, string $message = '', string $exception = '')
  * @method static void validTime(mixed $value, string $message = '', string $exception = '')
  * @method static void validToken(mixed $value, string $message = '', string $exception = '')
+ * @method static void validUnsignedLong(mixed $value, string $message = '', string $exception = '')
  * @method static void validYearMonth(mixed $value, string $message = '', string $exception = '')
  * @method static void nullOrValidAnyURI(mixed $value, string $message = '', string $exception = '')
  * @method static void nullOrValidBase64Binary(mixed $value, string $message = '', string $exception = '')
@@ -82,6 +83,7 @@
  * @method static void nullOrValidString(mixed $value, string $message = '', string $exception = '')
  * @method static void nullOrValidTime(mixed $value, string $message = '', string $exception = '')
  * @method static void nullOrValidToken(mixed $value, string $message = '', string $exception = '')
+ * @method static void nullOrValidUnsignedLong(mixed $value, string $message = '', string $exception = '')
  * @method static void nullOrValidYearMonth(mixed $value, string $message = '', string $exception = '')
  * @method static void allValidAnyURI(mixed $value, string $message = '', string $exception = '')
  * @method static void allValidBase64Binary(mixed $value, string $message = '', string $exception = '')
@@ -119,6 +121,7 @@
  * @method static void allValidString(mixed $value, string $message = '', string $exception = '')
  * @method static void allValidTime(mixed $value, string $message = '', string $exception = '')
  * @method static void allValidToken(mixed $value, string $message = '', string $exception = '')
+ * @method static void allValidUnsignedLong(mixed $value, string $message = '', string $exception = '')
  * @method static void allValidYearMonth(mixed $value, string $message = '', string $exception = '')
  */
 class Assert extends BaseAssert
@@ -159,5 +162,6 @@ class Assert extends BaseAssert
     use StringTrait;
     use TimeTrait;
     use TokenTrait;
+    use UnsignedLongTrait;
     use YearMonthTrait;
 }
diff --git a/src/Assert/UnsignedLongTrait.php b/src/Assert/UnsignedLongTrait.php
new file mode 100644
index 00000000..b36b9802
--- /dev/null
+++ b/src/Assert/UnsignedLongTrait.php
@@ -0,0 +1,30 @@
+<?php
+
+declare(strict_types=1);
+
+namespace SimpleSAML\XML\Assert;
+
+use InvalidArgumentException;
+
+/**
+ * @package simplesamlphp/xml-common
+ */
+trait UnsignedLongTrait
+{
+    /** @var string */
+    private static string $unsignedLong_regex = '/^([+]?[0]*)(?:[0-9]|[1-9][0-9]{1,19}|1000000000000000|10000000000000000|100000000000000000|1000000000000000000|1[0-8]000000000000000000|18[0-4]00000000000000000|184[0-4]0000000000000000|1844[0-6]000000000000000|18446[0-7]00000000000000|184467[0-4]0000000000000|1844674[0-4]000000000000|184467440[0-7]0000000000|1844674407[0-3]000000000|18446744073[0-7]00000000|1844674407370000000[0-9]|18446744073709[0-5]00000|184467440737095[0-5]0000|1844674407370955[0-2]000)$/D';
+
+    /**
+     * @param string $value
+     * @param string $message
+     */
+    protected static function validUnsignedLong(string $value, string $message = ''): void
+    {
+        parent::regex(
+            $value,
+            self::$unsignedLong_regex,
+            $message ?: '%s is not a valid xs:unsignedLong',
+            InvalidArgumentException::class,
+        );
+    }
+}
diff --git a/src/Type/UnsignedLongValue.php b/src/Type/UnsignedLongValue.php
new file mode 100644
index 00000000..5414e855
--- /dev/null
+++ b/src/Type/UnsignedLongValue.php
@@ -0,0 +1,26 @@
+<?php
+
+declare(strict_types=1);
+
+namespace SimpleSAML\XML\Type;
+
+use SimpleSAML\XML\Assert\Assert;
+use SimpleSAML\XML\Exception\SchemaViolationException;
+
+/**
+ * @package simplesaml/xml-common
+ */
+class UnsignedLongValue extends IntegerValue
+{
+    /**
+     * Validate the value.
+     *
+     * @param string $value
+     * @throws \SimpleSAML\XML\Exception\SchemaViolationException on failure
+     * @return void
+     */
+    protected function validateValue(string $value): void
+    {
+        Assert::validUnsignedLong($this->sanitizeValue($value), SchemaViolationException::class);
+    }
+}
diff --git a/tests/Assert/UnsignedLongTest.php b/tests/Assert/UnsignedLongTest.php
new file mode 100644
index 00000000..6955e594
--- /dev/null
+++ b/tests/Assert/UnsignedLongTest.php
@@ -0,0 +1,55 @@
+<?php
+
+declare(strict_types=1);
+
+namespace SimpleSAML\Test\XML\Assert;
+
+use PHPUnit\Framework\Attributes\CoversClass;
+use PHPUnit\Framework\Attributes\DataProvider;
+use PHPUnit\Framework\TestCase;
+use SimpleSAML\Assert\AssertionFailedException;
+use SimpleSAML\XML\Assert\Assert;
+
+/**
+ * Class \SimpleSAML\Test\XML\Assert\UnsignedLongTest
+ *
+ * @package simplesamlphp/xml-common
+ */
+#[CoversClass(Assert::class)]
+final class UnsignedLongTest extends TestCase
+{
+    /**
+     * @param boolean $shouldPass
+     * @param string $unsignedLong
+     */
+    #[DataProvider('provideUnsignedLong')]
+    public function testValidUnsignedLong(bool $shouldPass, string $unsignedLong): void
+    {
+        try {
+            Assert::validUnsignedLong($unsignedLong);
+            $this->assertTrue($shouldPass);
+        } catch (AssertionFailedException $e) {
+            $this->assertFalse($shouldPass);
+        }
+    }
+
+
+    /**
+     * @return array<string, array{0: bool, 1: string}>
+     */
+    public static function provideUnsignedLong(): array
+    {
+        return [
+            'empty' => [false, ''],
+            'valid positive integer' => [true, '18446744073709551615'],
+            'invalid positive out-of-bounds' => [true, '18446744073709551616'],
+            'valid signed positive integer' => [true, '+18446744073709551615'],
+            'valid zero' => [true, '0'],
+            'valid negative leading zeros' => [true, '0000000000000000000005'],
+            'invalid with fractional' => [false, '1.'],
+            'invalid with space' => [false, '12 34'],
+            'invalid negative' => [false, '-1'],
+            'invalid with thousands-delimiter' => [false, '1,234'],
+        ];
+    }
+}
diff --git a/tests/Type/UnsignedLongValueTest.php b/tests/Type/UnsignedLongValueTest.php
new file mode 100644
index 00000000..d5454a74
--- /dev/null
+++ b/tests/Type/UnsignedLongValueTest.php
@@ -0,0 +1,55 @@
+<?php
+
+declare(strict_types=1);
+
+namespace SimpleSAML\Test\XML\Type;
+
+use PHPUnit\Framework\Attributes\CoversClass;
+use PHPUnit\Framework\Attributes\DataProvider;
+use PHPUnit\Framework\TestCase;
+use SimpleSAML\XML\Exception\SchemaViolationException;
+use SimpleSAML\XML\Type\UnsignedLongValue;
+
+/**
+ * Class \SimpleSAML\Test\Type\UnsignedLongValueTest
+ *
+ * @package simplesamlphp/xml-common
+ */
+#[CoversClass(UnsignedLongValue::class)]
+final class UnsignedLongValueTest extends TestCase
+{
+    /**
+     * @param boolean $shouldPass
+     * @param string $unsignedLong
+     */
+    #[DataProvider('provideUnsignedLong')]
+    public function testUnsignedLong(bool $shouldPass, string $unsignedLong): void
+    {
+        try {
+            UnsignedLongValue::fromString($unsignedLong);
+            $this->assertTrue($shouldPass);
+        } catch (SchemaViolationException $e) {
+            $this->assertFalse($shouldPass);
+        }
+    }
+
+
+    /**
+     * @return array<string, array{0: bool, 1: string}>
+     */
+    public static function provideUnsignedLong(): array
+    {
+        return [
+            'empty' => [false, ''],
+            'valid positive integer' => [true, '18446744073709551615'],
+            'invalid positive out-of-bounds' => [true, '18446744073709551616'],
+            'valid signed positive integer' => [true, '+18446744073709551615'],
+            'valid zero' => [true, '0'],
+            'valid negative leading zeros' => [true, '0000000000000000000005'],
+            'invalid with fractional' => [false, '1.'],
+            'valid with whitespace collapse' => [true, " 1 234 \n"],
+            'invalid negative' => [false, '-1'],
+            'invalid with thousands-delimiter' => [false, '1,234'],
+        ];
+    }
+}