diff --git a/src/Base32.php b/src/Base32.php
new file mode 100644
index 0000000..fce6233
--- /dev/null
+++ b/src/Base32.php
@@ -0,0 +1,135 @@
+<?php declare(strict_types=1);
+
+namespace KDuma\BinaryTools;
+
+use InvalidArgumentException;
+
+/**
+ * Base32 encoder/decoder using a configurable alphabet (default RFC 4648 without padding).
+ */
+final class Base32
+{
+    public const DEFAULT_ALPHABET = 'ABCDEFGHIJKLMNOPQRSTUVWXYZ234567';
+
+    /** @var array<string, array<string, int>> */
+    private static array $decodeMaps = [];
+
+    /** @var array<string, bool> */
+    private static array $validatedAlphabets = [];
+
+    public static function toBase32(string $binary, string $alphabet = self::DEFAULT_ALPHABET): string
+    {
+        self::ensureValidAlphabet($alphabet);
+
+        if ($binary === '') {
+            return '';
+        }
+
+        $result = '';
+        $buffer = 0;
+        $bitsLeft = 0;
+        $length = strlen($binary);
+
+        for ($i = 0; $i < $length; $i++) {
+            $buffer = ($buffer << 8) | ord($binary[$i]);
+            $bitsLeft += 8;
+
+            while ($bitsLeft >= 5) {
+                $bitsLeft -= 5;
+                $index = ($buffer >> $bitsLeft) & 0x1F;
+                $result .= $alphabet[$index];
+            }
+        }
+
+        if ($bitsLeft > 0) {
+            $index = ($buffer << (5 - $bitsLeft)) & 0x1F;
+            $result .= $alphabet[$index];
+        }
+
+        return $result;
+    }
+
+    public static function fromBase32(string $base32, string $alphabet = self::DEFAULT_ALPHABET): string
+    {
+        if ($base32 === '') {
+            return '';
+        }
+
+        $map = self::decodeMap($alphabet);
+
+        $buffer = 0;
+        $bitsLeft = 0;
+        $output = '';
+        $length = strlen($base32);
+
+        for ($i = 0; $i < $length; $i++) {
+            $char = $base32[$i];
+
+            if ($char === '=') {
+                break; // padding reached (RFC 4648)
+            }
+
+            if (!isset($map[$char])) {
+                throw new InvalidArgumentException(
+                    sprintf(
+                        "Invalid character '%s' at position %d in Base32 input.",
+                        $char,
+                        $i
+                    )
+                );
+            }
+
+            $buffer = ($buffer << 5) | $map[$char];
+            $bitsLeft += 5;
+
+            if ($bitsLeft >= 8) {
+                $bitsLeft -= 8;
+                $output .= chr(($buffer >> $bitsLeft) & 0xFF);
+            }
+        }
+
+        return $output;
+    }
+
+    /**
+     * @return array<string, int>
+     */
+    private static function decodeMap(string $alphabet): array
+    {
+        if (!isset(self::$decodeMaps[$alphabet])) {
+            self::ensureValidAlphabet($alphabet);
+
+            $map = [];
+            for ($i = 0; $i < 32; $i++) {
+                $char = $alphabet[$i];
+                $map[$char] = $i;
+            }
+
+            self::$decodeMaps[$alphabet] = $map;
+        }
+
+        return self::$decodeMaps[$alphabet];
+    }
+
+    private static function ensureValidAlphabet(string $alphabet): void
+    {
+        if (isset(self::$validatedAlphabets[$alphabet])) {
+            return;
+        }
+
+        if (strlen($alphabet) !== 32) {
+            throw new InvalidArgumentException('Base32 alphabet must contain exactly 32 characters.');
+        }
+
+        $characters = [];
+        for ($i = 0; $i < 32; $i++) {
+            $char = $alphabet[$i];
+            if (isset($characters[$char])) {
+                throw new InvalidArgumentException('Base32 alphabet must contain unique characters.');
+            }
+            $characters[$char] = true;
+        }
+
+        self::$validatedAlphabets[$alphabet] = true;
+    }
+}
diff --git a/src/BinaryString.php b/src/BinaryString.php
index 18e0e7b..da928aa 100644
--- a/src/BinaryString.php
+++ b/src/BinaryString.php
@@ -23,6 +23,17 @@ public function toBase64(): string
         return base64_encode($this->value);
     }
 
+    /**
+     * Returns a Base32-encoded string representation of the binary value.
+     *
+     * @param string $alphabet The alphabet to use for Base32 encoding.
+     * @return string The Base32-encoded string.
+     */
+    public function toBase32(string $alphabet = Base32::DEFAULT_ALPHABET): string
+    {
+        return Base32::toBase32($this->value, $alphabet);
+    }
+
     public function size(): int
     {
         return strlen($this->value);
@@ -43,6 +54,18 @@ public static function fromBase64(string $base64): static
         return new static(base64_decode($base64, true));
     }
 
+    /**
+     * Decodes a Base32-encoded string to a BinaryString instance.
+     *
+     * @param string $base32 The Base32-encoded string to decode.
+     * @param string $alphabet The alphabet used for Base32 encoding. Defaults to Base32::DEFAULT_ALPHABET.
+     * @return static A new BinaryString instance containing the decoded binary data.
+     */
+    public static function fromBase32(string $base32, string $alphabet = Base32::DEFAULT_ALPHABET): static
+    {
+        return new static(Base32::fromBase32($base32, $alphabet));
+    }
+
     public function equals(BinaryString $other): bool
     {
         return hash_equals($this->value, $other->value);
diff --git a/tests/Base32Test.php b/tests/Base32Test.php
new file mode 100644
index 0000000..a37d0b7
--- /dev/null
+++ b/tests/Base32Test.php
@@ -0,0 +1,138 @@
+<?php declare(strict_types=1);
+
+namespace KDuma\BinaryTools\Tests;
+
+use KDuma\BinaryTools\Base32;
+use KDuma\BinaryTools\BinaryString;
+use PHPUnit\Framework\Attributes\CoversClass;
+use PHPUnit\Framework\Attributes\DataProvider;
+use PHPUnit\Framework\TestCase;
+
+#[CoversClass(Base32::class)]
+class Base32Test extends TestCase
+{
+    public function testEmpty(): void
+    {
+        $this->assertSame('', Base32::toBase32(''));
+        $this->assertSame('', Base32::fromBase32(''));
+
+        $binaryString = BinaryString::fromString('');
+        $this->assertSame('', $binaryString->toBase32());
+        $this->assertTrue($binaryString->equals(BinaryString::fromBase32('')));
+    }
+
+    /**
+     * RFC 4648 test vectors (uppercase, unpadded form).
+     *
+     * @return array<string, array{plain: string, base32: string}>
+     */
+    public static function vectors(): array
+    {
+        return [
+            'f' => ['plain' => 'f',       'base32' => 'MY'],
+            'fo' => ['plain' => 'fo',      'base32' => 'MZXQ'],
+            'foo' => ['plain' => 'foo',     'base32' => 'MZXW6'],
+            'foob' => ['plain' => 'foob',    'base32' => 'MZXW6YQ'],
+            'fooba' => ['plain' => 'fooba',   'base32' => 'MZXW6YTB'],
+            'foobar' => ['plain' => 'foobar',  'base32' => 'MZXW6YTBOI'],
+            'A' => ['plain' => 'A',       'base32' => 'IE'],
+            'AB' => ['plain' => 'AB',      'base32' => 'IFBA'],
+            'ABC' => ['plain' => 'ABC',     'base32' => 'IFBEG'],
+        ];
+    }
+
+    #[DataProvider('vectors')]
+    public function testToBase32MatchesKnownVectors(string $plain, string $base32): void
+    {
+        $this->assertSame($base32, Base32::toBase32($plain));
+        $this->assertSame($base32, BinaryString::fromString($plain)->toBase32());
+    }
+
+    #[DataProvider('vectors')]
+    public function testFromBase32MatchesKnownVectors(string $plain, string $base32): void
+    {
+        $this->assertSame($plain, Base32::fromBase32($base32));
+        $this->assertTrue(BinaryString::fromString($plain)->equals(BinaryString::fromBase32($base32)));
+    }
+
+    public function testRoundTripRandomBinary(): void
+    {
+        $lengths = [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 16, 31, 32, 33, 64, 100, 256, 1024];
+
+        foreach ($lengths as $length) {
+            $binary = ($length === 0) ? '' : random_bytes($length);
+            $encoded = Base32::toBase32($binary);
+            $decoded = Base32::fromBase32($encoded);
+
+            $this->assertSame($binary, $decoded, "Failed round-trip at length {$length}");
+        }
+    }
+
+    public function testDecodeThenEncodeIsIdempotent(): void
+    {
+        $original = 'MZXW6YTBOI'; // "foobar"
+        $decoded = Base32::fromBase32($original);
+        $reEncoded = Base32::toBase32($decoded);
+
+        $this->assertSame($original, $reEncoded);
+    }
+
+    public function testLowercaseInputThrowsException(): void
+    {
+        $lower = 'mzxw6ytboi';
+
+        $this->expectException(\InvalidArgumentException::class);
+        $this->expectExceptionMessage("Invalid character 'm' at position 0 in Base32 input.");
+
+        Base32::fromBase32($lower);
+    }
+
+    public function testCustomAlphabet(): void
+    {
+        $customAlphabet = '0123456789ABCDEFGHIJKLMNOPQRSTUV';
+        $data = 'Hello World';
+
+        $encoded = Base32::toBase32($data, $customAlphabet);
+        $decoded = Base32::fromBase32($encoded, $customAlphabet);
+
+        $this->assertSame($data, $decoded);
+    }
+
+    public function testInvalidAlphabetLengthThrowsException(): void
+    {
+        $shortAlphabet = 'ABCDEFGHIJKLMNOPQRSTUVWXYZ12345'; // 31 chars instead of 32
+
+        $this->expectException(\InvalidArgumentException::class);
+        $this->expectExceptionMessage('Base32 alphabet must contain exactly 32 characters.');
+
+        Base32::toBase32('test', $shortAlphabet);
+    }
+
+    public function testDuplicateCharactersInAlphabetThrowsException(): void
+    {
+        $duplicateAlphabet = 'ABCDEFGHIJKLMNOPQRSTUVWXYZ23456A'; // 'A' appears twice
+
+        $this->expectException(\InvalidArgumentException::class);
+        $this->expectExceptionMessage('Base32 alphabet must contain unique characters.');
+
+        Base32::toBase32('test', $duplicateAlphabet);
+    }
+
+    public function testPaddingIsIgnoredDuringDecoding(): void
+    {
+        $paddedBase32 = 'MZXW6YTBOI======'; // "foobar" with padding
+        $decoded = Base32::fromBase32($paddedBase32);
+
+        $this->assertSame('foobar', $decoded);
+    }
+
+    public function testInvalidCharacterInMiddleThrowsException(): void
+    {
+        $invalidBase32 = 'MZXW@YTBOI'; // '@' is invalid
+
+        $this->expectException(\InvalidArgumentException::class);
+        $this->expectExceptionMessage("Invalid character '@' at position 4 in Base32 input.");
+
+        Base32::fromBase32($invalidBase32);
+    }
+}
diff --git a/tests/BinaryStringTest.php b/tests/BinaryStringTest.php
index 3141092..f18f4cb 100644
--- a/tests/BinaryStringTest.php
+++ b/tests/BinaryStringTest.php
@@ -64,4 +64,18 @@ public function testEquals()
         $this->assertTrue($this->binaryString->equals(BinaryString::fromString("\x01\x02\x03\x04")));
         $this->assertFalse($this->binaryString->equals(BinaryString::fromString("\xFF\xFF\xFF\xFF")));
     }
+
+    public function testToBase32()
+    {
+        $binaryString = BinaryString::fromString("foobar");
+        $this->assertEquals("MZXW6YTBOI", $binaryString->toBase32());
+    }
+
+    public function testFromBase32()
+    {
+        $reconstructedString = BinaryString::fromBase32("MZXW6YTBOI");
+        $expected = BinaryString::fromString("foobar");
+
+        $this->assertTrue($expected->equals($reconstructedString));
+    }
 }