The Sikorsky SH-3 Sea King (company designation S-61) is a twin-engined anti-submarine warfare (ASW) helicopter. It was a landmark design, being the first ASW helicopter to take advantage of turboshaft engines, as well as being the first amphibious helicopter in the world. Introduced in 1961, it served with the United States Navy, and remains in service in many countries around the world. The Sea King has been built under license in Italy and Japan, and in the United Kingdom as the Westland Sea King. The major civil versions are the S-61L and S-61N.