diff --git a/src/ggT/ggT.c b/src/ggT/ggT.c
new file mode 100644
index 0000000..ef9b8ef
--- /dev/null
+++ b/src/ggT/ggT.c
@@ -0,0 +1,16 @@
+#include <stdio.h>
+
+
+int ggT(int a, int b){
+    // handles the zero cases
+    if(a == 0) return b;
+    if(b == 0) return a;
+
+    // Euclidean algorithm with modulo for getting the ggT
+    while (b != 0) {
+        int temp = b;
+        b = a % b;
+        a = temp;
+    }
+    return a;
+}
\ No newline at end of file
diff --git a/src/ggT/ggT.h b/src/ggT/ggT.h
new file mode 100644
index 0000000..4dc2850
--- /dev/null
+++ b/src/ggT/ggT.h
@@ -0,0 +1,6 @@
+#ifndef GGT_H
+#define GGT_H
+
+int ggT(int a, int b);
+
+#endif
diff --git a/test/ggT/test_ggT.c b/test/ggT/test_ggT.c
new file mode 100644
index 0000000..6c14258
--- /dev/null
+++ b/test/ggT/test_ggT.c
@@ -0,0 +1,70 @@
+#include "unity.h"
+#include "ggT.h"
+
+void setUp(){}
+void tearDown(){}
+
+void test_ggTOf5And10(){
+    //arrange
+    int a = 5;
+    int b = 10;
+    int expected = 5;
+
+    //act
+    int result = ggT(a,b);
+
+    //assert
+    TEST_ASSERT_EQUAL_INT(expected, result);
+}
+
+void test_ggTOfFirstNumberZero(){
+    //arrange
+    int a = 0;
+    int b = 5;
+    int expected = 5;
+
+    //act
+    int result = ggT(a,b);
+
+    //assert
+    TEST_ASSERT_EQUAL_INT(expected, result);
+}
+
+void test_ggTOfSecondNumberZero(){
+    //arrange
+    int a = 10;
+    int b = 0;
+    int expected = 10;
+
+    //act
+    int result = ggT(a,b);
+
+    //assert
+    TEST_ASSERT_EQUAL_INT(expected, result);
+}
+
+void test_ggTOfBothNumbersZero(){
+    //arrange
+    int a = 0;
+    int b = 0;
+    int expected = 0;
+
+    //act
+    int result = ggT(a,b);
+
+    //assert
+    TEST_ASSERT_EQUAL_INT(expected,result);
+}
+
+void test_ggTOfCoprimes(){
+    //arrange
+    int a = 13;
+    int b = 27;
+    int expected = 1;
+
+    //act
+    int result = ggT(a,b);
+
+    //assert
+    TEST_ASSERT_EQUAL_INT(expected,result);
+}
\ No newline at end of file