John Adolphus Bernard Dahlgren (November 13, 1809 – July 12, 1870) was a United States Navy officer who founded his service's Ordnance Department and launched major advances in gunnery. Dahlgren devised a smoothbore howitzer, adaptable for many sizes of craft as well as shore installations. He then introduced a cast-iron muzzle-loading cannon with vastly increased range and accuracy, known as the Dahlgren gun, that became the Navy's standard armament.