The 16"/50 caliber Mark 7 – United States Naval Gun is the main armament of the Iowa-class battleships and was the planned main armament of the cancelled Montana-class battleship.

The Iowa class was a class of six fast battleships ordered by the United States Navy in 1939 and 1940. They were initially intended to intercept fast capital ships such as the Japanese Kongō class and also serve as the "fast wing" in a traditional battle line alongside slower battleships. The Iowa class was designed to meet the Second London Naval Treaty's "escalator clause" limit of 45,000-long-ton (45,700 t) standard displacement. Beginning in August 1942, four vessels, Iowa, New Jersey, Missouri, and Wisconsin, were completed; two more, Illinois and Kentucky, were laid down but canceled in 1945 and 1958, respectively, before completion, and both hulls were scrapped in 1958–1959.