diff --git a/src/main/java/com/thealgorithms/ciphers/PermutationCipher.java b/src/main/java/com/thealgorithms/ciphers/PermutationCipher.java
new file mode 100644
index 000000000000..ce443545db1d
--- /dev/null
+++ b/src/main/java/com/thealgorithms/ciphers/PermutationCipher.java
@@ -0,0 +1,194 @@
+package com.thealgorithms.ciphers;
+
+import java.util.HashSet;
+import java.util.Set;
+
+/**
+ * A Java implementation of Permutation Cipher.
+ * It is a type of transposition cipher in which the plaintext is divided into blocks
+ * and the characters within each block are rearranged according to a fixed permutation key.
+ *
+ * For example, with key {3, 1, 2} and plaintext "HELLO", the text is divided into blocks
+ * of 3 characters: "HEL" and "LO" (with padding). The characters are then rearranged
+ * according to the key positions.
+ *
+ * @author GitHub Copilot
+ */
+public class PermutationCipher {
+
+    private static final char PADDING_CHAR = 'X';
+
+    /**
+     * Encrypts the given plaintext using the permutation cipher with the specified key.
+     *
+     * @param plaintext the text to encrypt
+     * @param key the permutation key (array of integers representing positions)
+     * @return the encrypted text
+     * @throws IllegalArgumentException if the key is invalid
+     */
+    public String encrypt(String plaintext, int[] key) {
+        validateKey(key);
+
+        if (plaintext == null || plaintext.isEmpty()) {
+            return plaintext;
+        }
+
+        // Remove spaces and convert to uppercase for consistent processing
+        String cleanText = plaintext.replaceAll("\\s+", "").toUpperCase();
+
+        // Pad the text to make it divisible by key length
+        String paddedText = padText(cleanText, key.length);
+
+        StringBuilder encrypted = new StringBuilder();
+
+        // Process text in blocks of key length
+        for (int i = 0; i < paddedText.length(); i += key.length) {
+            String block = paddedText.substring(i, Math.min(i + key.length, paddedText.length()));
+            encrypted.append(permuteBlock(block, key));
+        }
+
+        return encrypted.toString();
+    }
+
+    /**
+     * Decrypts the given ciphertext using the permutation cipher with the specified key.
+     *
+     * @param ciphertext the text to decrypt
+     * @param key the permutation key (array of integers representing positions)
+     * @return the decrypted text
+     * @throws IllegalArgumentException if the key is invalid
+     */
+    public String decrypt(String ciphertext, int[] key) {
+        validateKey(key);
+
+        if (ciphertext == null || ciphertext.isEmpty()) {
+            return ciphertext;
+        }
+
+        // Create the inverse permutation
+        int[] inverseKey = createInverseKey(key);
+
+        StringBuilder decrypted = new StringBuilder();
+
+        // Process text in blocks of key length
+        for (int i = 0; i < ciphertext.length(); i += key.length) {
+            String block = ciphertext.substring(i, Math.min(i + key.length, ciphertext.length()));
+            decrypted.append(permuteBlock(block, inverseKey));
+        }
+
+        // Remove padding characters from the end
+        return removePadding(decrypted.toString());
+    }
+    /**
+     * Validates that the permutation key is valid.
+     * A valid key must contain all integers from 1 to n exactly once, where n is the key length.
+     *
+     * @param key the permutation key to validate
+     * @throws IllegalArgumentException if the key is invalid
+     */
+    private void validateKey(int[] key) {
+        if (key == null || key.length == 0) {
+            throw new IllegalArgumentException("Key cannot be null or empty");
+        }
+
+        Set<Integer> keySet = new HashSet<>();
+        for (int position : key) {
+            if (position < 1 || position > key.length) {
+                throw new IllegalArgumentException("Key must contain integers from 1 to " + key.length);
+            }
+            if (!keySet.add(position)) {
+                throw new IllegalArgumentException("Key must contain each position exactly once");
+            }
+        }
+    }
+
+    /**
+     * Pads the text with padding characters to make its length divisible by the block size.
+     *
+     * @param text the text to pad
+     * @param blockSize the size of each block
+     * @return the padded text
+     */
+    private String padText(String text, int blockSize) {
+        int remainder = text.length() % blockSize;
+        if (remainder == 0) {
+            return text;
+        }
+
+        int paddingNeeded = blockSize - remainder;
+        StringBuilder padded = new StringBuilder(text);
+        for (int i = 0; i < paddingNeeded; i++) {
+            padded.append(PADDING_CHAR);
+        }
+
+        return padded.toString();
+    }
+    /**
+     * Applies the permutation to a single block of text.
+     *
+     * @param block the block to permute
+     * @param key the permutation key
+     * @return the permuted block
+     */
+    private String permuteBlock(String block, int[] key) {
+        if (block.length() != key.length) {
+            // Handle case where block is shorter than key (shouldn't happen with proper padding)
+            block = padText(block, key.length);
+        }
+
+        char[] result = new char[key.length];
+        char[] blockChars = block.toCharArray();
+
+        for (int i = 0; i < key.length; i++) {
+            // Key positions are 1-based, so subtract 1 for 0-based array indexing
+            result[i] = blockChars[key[i] - 1];
+        }
+
+        return new String(result);
+    }
+
+    /**
+     * Creates the inverse permutation key for decryption.
+     *
+     * @param key the original permutation key
+     * @return the inverse key
+     */
+    private int[] createInverseKey(int[] key) {
+        int[] inverse = new int[key.length];
+
+        for (int i = 0; i < key.length; i++) {
+            // The inverse key maps each position to where it should go
+            inverse[key[i] - 1] = i + 1;
+        }
+
+        return inverse;
+    }
+
+    /**
+     * Removes padding characters from the end of the decrypted text.
+     *
+     * @param text the text to remove padding from
+     * @return the text without padding
+     */
+    private String removePadding(String text) {
+        if (text.isEmpty()) {
+            return text;
+        }
+
+        int i = text.length() - 1;
+        while (i >= 0 && text.charAt(i) == PADDING_CHAR) {
+            i--;
+        }
+
+        return text.substring(0, i + 1);
+    }
+
+    /**
+     * Gets the padding character used by this cipher.
+     *
+     * @return the padding character
+     */
+    public char getPaddingChar() {
+        return PADDING_CHAR;
+    }
+}
diff --git a/src/test/java/com/thealgorithms/ciphers/PermutationCipherTest.java b/src/test/java/com/thealgorithms/ciphers/PermutationCipherTest.java
new file mode 100644
index 000000000000..4ba6787cc97e
--- /dev/null
+++ b/src/test/java/com/thealgorithms/ciphers/PermutationCipherTest.java
@@ -0,0 +1,323 @@
+package com.thealgorithms.ciphers;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertThrows;
+
+import org.junit.jupiter.api.Test;
+
+class PermutationCipherTest {
+
+    private final PermutationCipher cipher = new PermutationCipher();
+
+    @Test
+    void testBasicEncryption() {
+        // given
+        String plaintext = "HELLO";
+        int[] key = {3, 1, 2}; // Move 3rd position to 1st, 1st to 2nd, 2nd to 3rd
+
+        // when
+        String encrypted = cipher.encrypt(plaintext, key);
+
+        // then
+        // "HELLO" becomes "HEL" + "LOX" (padded)
+        // "HEL" with key {3,1,2} becomes "LHE" (L=3rd, H=1st, E=2nd)
+        // "LOX" with key {3,1,2} becomes "XLO" (X=3rd, L=1st, O=2nd)
+        assertEquals("LHEXLO", encrypted);
+    }
+
+    @Test
+    void testBasicDecryption() {
+        // given
+        String ciphertext = "LHEXLO";
+        int[] key = {3, 1, 2};
+
+        // when
+        String decrypted = cipher.decrypt(ciphertext, key);
+
+        // then
+        assertEquals("HELLO", decrypted);
+    }
+
+    @Test
+    void testEncryptDecryptRoundTrip() {
+        // given
+        String plaintext = "THIS IS A TEST MESSAGE";
+        int[] key = {4, 2, 1, 3};
+
+        // when
+        String encrypted = cipher.encrypt(plaintext, key);
+        String decrypted = cipher.decrypt(encrypted, key);
+
+        // then
+        assertEquals("THISISATESTMESSAGE", decrypted); // Spaces are removed during encryption
+    }
+
+    @Test
+    void testSingleCharacterKey() {
+        // given
+        String plaintext = "ABCDEF";
+        int[] key = {1}; // Identity permutation
+
+        // when
+        String encrypted = cipher.encrypt(plaintext, key);
+        String decrypted = cipher.decrypt(encrypted, key);
+
+        // then
+        assertEquals("ABCDEF", encrypted); // Should remain unchanged
+        assertEquals("ABCDEF", decrypted);
+    }
+
+    @Test
+    void testLargerKey() {
+        // given
+        String plaintext = "PERMUTATION";
+        int[] key = {5, 3, 1, 4, 2}; // 5-character permutation
+
+        // when
+        String encrypted = cipher.encrypt(plaintext, key);
+        String decrypted = cipher.decrypt(encrypted, key);
+
+        // then
+        assertEquals("PERMUTATION", decrypted);
+    }
+
+    @Test
+    void testExactBlockSize() {
+        // given
+        String plaintext = "ABCDEF"; // Length 6, divisible by key length 3
+        int[] key = {2, 3, 1};
+
+        // when
+        String encrypted = cipher.encrypt(plaintext, key);
+        String decrypted = cipher.decrypt(encrypted, key);
+
+        // then
+        assertEquals("ABCDEF", decrypted);
+    }
+
+    @Test
+    void testEmptyString() {
+        // given
+        String plaintext = "";
+        int[] key = {2, 1, 3};
+
+        // when
+        String encrypted = cipher.encrypt(plaintext, key);
+        String decrypted = cipher.decrypt(encrypted, key);
+
+        // then
+        assertEquals("", encrypted);
+        assertEquals("", decrypted);
+    }
+
+    @Test
+    void testNullString() {
+        // given
+        String plaintext = null;
+        int[] key = {2, 1, 3};
+
+        // when
+        String encrypted = cipher.encrypt(plaintext, key);
+        String decrypted = cipher.decrypt(encrypted, key);
+
+        // then
+        assertEquals(null, encrypted);
+        assertEquals(null, decrypted);
+    }
+
+    @Test
+    void testStringWithSpaces() {
+        // given
+        String plaintext = "A B C D E F";
+        int[] key = {2, 1};
+
+        // when
+        String encrypted = cipher.encrypt(plaintext, key);
+        String decrypted = cipher.decrypt(encrypted, key);
+
+        // then
+        assertEquals("ABCDEF", decrypted); // Spaces should be removed
+    }
+
+    @Test
+    void testLowercaseConversion() {
+        // given
+        String plaintext = "hello world";
+        int[] key = {3, 1, 2};
+
+        // when
+        String encrypted = cipher.encrypt(plaintext, key);
+        String decrypted = cipher.decrypt(encrypted, key);
+
+        // then
+        assertEquals("HELLOWORLD", decrypted); // Should be converted to uppercase
+    }
+
+    @Test
+    void testInvalidKeyNull() {
+        // given
+        String plaintext = "HELLO";
+        int[] key = null;
+
+        // when & then
+        assertThrows(IllegalArgumentException.class, () -> cipher.encrypt(plaintext, key));
+        assertThrows(IllegalArgumentException.class, () -> cipher.decrypt(plaintext, key));
+    }
+
+    @Test
+    void testInvalidKeyEmpty() {
+        // given
+        String plaintext = "HELLO";
+        int[] key = {};
+
+        // when & then
+        assertThrows(IllegalArgumentException.class, () -> cipher.encrypt(plaintext, key));
+        assertThrows(IllegalArgumentException.class, () -> cipher.decrypt(plaintext, key));
+    }
+
+    @Test
+    void testInvalidKeyOutOfRange() {
+        // given
+        String plaintext = "HELLO";
+        int[] key = {1, 2, 4}; // 4 is out of range for key length 3
+
+        // when & then
+        assertThrows(IllegalArgumentException.class, () -> cipher.encrypt(plaintext, key));
+        assertThrows(IllegalArgumentException.class, () -> cipher.decrypt(plaintext, key));
+    }
+
+    @Test
+    void testInvalidKeyZero() {
+        // given
+        String plaintext = "HELLO";
+        int[] key = {0, 1, 2}; // 0 is invalid (should be 1-based)
+
+        // when & then
+        assertThrows(IllegalArgumentException.class, () -> cipher.encrypt(plaintext, key));
+        assertThrows(IllegalArgumentException.class, () -> cipher.decrypt(plaintext, key));
+    }
+
+    @Test
+    void testInvalidKeyDuplicate() {
+        // given
+        String plaintext = "HELLO";
+        int[] key = {1, 2, 2}; // Duplicate position
+
+        // when & then
+        assertThrows(IllegalArgumentException.class, () -> cipher.encrypt(plaintext, key));
+        assertThrows(IllegalArgumentException.class, () -> cipher.decrypt(plaintext, key));
+    }
+
+    @Test
+    void testInvalidKeyMissingPosition() {
+        // given
+        String plaintext = "HELLO";
+        int[] key = {1, 3}; // Missing position 2
+
+        // when & then
+        assertThrows(IllegalArgumentException.class, () -> cipher.encrypt(plaintext, key));
+        assertThrows(IllegalArgumentException.class, () -> cipher.decrypt(plaintext, key));
+    }
+
+    @Test
+    void testReverseKey() {
+        // given
+        String plaintext = "ABCD";
+        int[] key = {4, 3, 2, 1}; // Reverse order
+
+        // when
+        String encrypted = cipher.encrypt(plaintext, key);
+        String decrypted = cipher.decrypt(encrypted, key);
+
+        // then
+        assertEquals("DCBA", encrypted); // Should be reversed
+        assertEquals("ABCD", decrypted);
+    }
+
+    @Test
+    void testSpecificExampleFromDescription() {
+        // given
+        String plaintext = "HELLO";
+        int[] key = {3, 1, 2};
+
+        // when
+        String encrypted = cipher.encrypt(plaintext, key);
+
+        // then
+        // Block 1: "HEL" -> positions {3,1,2} -> "LHE"
+        // Block 2: "LOX" -> positions {3,1,2} -> "XLO"
+        assertEquals("LHEXLO", encrypted);
+        // Verify decryption
+        String decrypted = cipher.decrypt(encrypted, key);
+        assertEquals("HELLO", decrypted);
+    }
+
+    @Test
+    void testPaddingCharacterGetter() {
+        // when
+        char paddingChar = cipher.getPaddingChar();
+
+        // then
+        assertEquals('X', paddingChar);
+    }
+
+    @Test
+    void testLongText() {
+        // given
+        String plaintext = "THE QUICK BROWN FOX JUMPS OVER THE LAZY DOG";
+        int[] key = {4, 1, 3, 2};
+
+        // when
+        String encrypted = cipher.encrypt(plaintext, key);
+        String decrypted = cipher.decrypt(encrypted, key);
+
+        // then
+        assertEquals("THEQUICKBROWNFOXJUMPSOVERTHELAZYDOG", decrypted);
+    }
+
+    @Test
+    void testIdentityPermutation() {
+        // given
+        String plaintext = "IDENTITY";
+        int[] key = {1, 2, 3, 4}; // Identity permutation
+
+        // when
+        String encrypted = cipher.encrypt(plaintext, key);
+        String decrypted = cipher.decrypt(encrypted, key);
+
+        // then
+        assertEquals("IDENTITY", encrypted); // Should remain unchanged
+        assertEquals("IDENTITY", decrypted);
+    }
+
+    @Test
+    void testEmptyStringRemovePadding() {
+        // given - Test to cover line 178 (empty string case in removePadding)
+        String ciphertext = "";
+        int[] key = {2, 1, 3};
+
+        // when
+        String decrypted = cipher.decrypt(ciphertext, key);
+
+        // then
+        assertEquals("", decrypted); // Should return empty string directly
+    }
+
+    @Test
+    void testBlockShorterThanKey() {
+        // given - Test to cover line 139 (block length != key length case)
+        // This is a defensive case where permuteBlock might receive a block shorter than key
+        // We can test this by manually creating a scenario with malformed ciphertext
+        String malformedCiphertext = "AB"; // Length 2, but key length is 3
+        int[] key = {3, 1, 2}; // Key length is 3
+
+        // when - This should trigger the padding logic in permuteBlock during decryption
+        String decrypted = cipher.decrypt(malformedCiphertext, key);
+
+        // then - The method should handle the short block gracefully
+        // "AB" gets padded to "ABX", then permuted with inverse key {2,3,1}
+        // inverse key {2,3,1} means: pos 2→1st, pos 3→2nd, pos 1→3rd = "BXA"
+        // Padding removal only removes trailing X's, so "BXA" remains as is
+        assertEquals("BXA", decrypted);
+    }
+}