Ordnance is a ghost town in Umatilla County, Oregon, United States, southwest of Hermiston on Interstate 84/U.S. Route 30, near the intersection with Interstate 82. According to Oregon Geographic Names, the United States Department of War commissioned the establishment of Umatilla Ordnance Depot (renamed Umatilla Army Depot and currently Umatilla Chemical Depot) in northern Umatilla County in 1941. The town was named after the depot, and Ordnance post office was established in 1943. By the 1960s, Ordnance was no longer a community.