The 4.5 inch gun M1 was a field gun developed in the United States in the beginning of World War II. It shared the same carriage with the 155mm Howitzer M1 and fired the same ammunition as the British BL 4.5 inch Medium Field Gun. Beginning in 1944, the weapon was used by the U.S. Army as corps-level artillery; with the end of hostilities, it was declared obsolete.