An anti-ship missile (AShM) is a guided missile that is designed for use against ships and large boats. Most anti-ship missiles are of the sea skimming variety, and many use a combination of inertial guidance and active radar homing. A large number of other anti-ship missiles use infrared homing to follow the heat that is emitted by a ship; it is also possible for anti-ship missiles to be guided by radio command all the way.
The first anti-ship missiles, which were developed and built by Nazi Germany, used radio command guidance. These saw some success in the Mediterranean Theatre during 1943–44, sinking or heavily damaging at least 31 ships with the Henschel Hs 293 and more than seven with the Fritz X, including the Italian battleship Roma and the light cruiser . A variant of the HS 293 had a TV camera/transmitter on board. The bomber carrying it could then fly outside the range of naval anti-aircraft guns and use visual guidance via the bombardier to lead the missile to its target by radio control.
Many anti-ship missiles can be launched from a variety of weapons systems including surface warships (also referred to as ship-to-ship missiles), submarines, bombers, fighter planes, patrol planes, helicopters, shore batteries, land vehicles, and, conceivably, even infantrymen firing shoulder-launched missiles. The term surface-to-surface missile (SSM) is used when appropriate. The longer-range anti-ship missiles are often called anti-ship cruise missiles.
A typical abbreviation for the phrase "anti-ship missile" is AShM or ASHM, used to avoid confusion with air-to-surface missiles (ASMs), anti-submarine missiles (anti-submarine warfare missiles (ASWMs)), and anti-satellite missiles (ASatMs or ASATMs).
Anti-ship missiles were among the first instances of short-range guided weapons during the Second World War in 1943–1944. The German Luftwaffe used the Hs 293, the Fritz X, as well as others missiles, launched from its bombers, with deadly effect against some Allied ships.