diff --git a/DIRECTORY.md b/DIRECTORY.md
index 7b41432b..850be426 100644
--- a/DIRECTORY.md
+++ b/DIRECTORY.md
@@ -47,6 +47,7 @@
   * [Quicksort](./Sorting/QuickSort.php)
   * [Radixsort](./Sorting/RadixSort.php)
   * [Selectionsort](./Sorting/SelectionSort.php)
+  * [Shellsort](./Sorting/ShellSort.php)
 
 ## Strings
   * [Checkanagram](./Strings/CheckAnagram.php)
@@ -75,6 +76,7 @@
   * Sorting
     * [Arraykeyssorttest](./tests/Sorting/ArrayKeysSortTest.php)
     * [Sortingtests](./tests/Sorting/SortingTests.php)
+    * [Shelltest](./tests/Sorting/ShellSortTest.php)
   * Strings
     * [Stringstest](./tests/Strings/StringsTest.php)
 
diff --git a/Sorting/ShellSort.php b/Sorting/ShellSort.php
new file mode 100644
index 00000000..cf9f915c
--- /dev/null
+++ b/Sorting/ShellSort.php
@@ -0,0 +1,31 @@
+<?php
+
+/** Shell sort is an in-place comparison sort.
+   * Starting with pairs of items that are far off from one another, the approach gradually closes the distance between the elements to be compared. 
+   * Some out-of-place components may be brought into position more quickly than with a basic closest neighbour exchange by starting with far-off elements.
+
+   * @param array $array 
+   * @param $a
+   * @param $b
+   * @return array $array*/
+
+function shellSort($array)
+{
+	$a = round(count($array)/2);
+	while($a > 0)
+	{
+		for($b = $a; $b < count($array);$b++){
+			$temp = $array[$b];
+			$i = $b;
+			while($i >= $a && $array[$i-$a] > $temp)
+			{
+				$array[$i] = $array[$i - $a];
+				$i -= $a;
+			}
+			$array[$i] = $temp;
+		}
+		$a = round($a/2.2);
+	}
+	return $array;
+}
+?>
diff --git a/tests/Sorting/ShellSortTest.php b/tests/Sorting/ShellSortTest.php
new file mode 100644
index 00000000..e6c12932
--- /dev/null
+++ b/tests/Sorting/ShellSortTest.php
@@ -0,0 +1,24 @@
+<?php
+
+require_once __DIR__ . '/../../vendor/autoload.php';
+require_once __DIR__ . '/../../Sorting/ShellSort.php';
+
+use PHPUnit\Framework\TestCase;
+
+class shellSortTest extends TestCase
+{
+    public function testShellSort() 
+    {
+        $array = array(2, 1, 6, 3, 0, 9, 5);
+        $sorted = shellSort($array);
+        $this->assertEquals([0, 1, 2, 3, 5, 6, 9], $sorted);
+    }
+
+    public function testShellSort2() 
+    {
+        $array = array(7, 9, 1, 6, 2, 5, 0));
+        $sorted = shellSort($array);
+        $this->assertEquals([0, 1, 2, 5, 6, 7, 9], $sorted);
+    }
+
+}
\ No newline at end of file