thumb|RIM-161 of the United States Navy
A Surface to Air Missile (SAM) or ground-to-air missile (GTAM) is a missile designed to be launched from the ground to destroy aircraft. It is a type of anti-aircraft system.

Land-based SAMs can be deployed from fixed installations or mobile launchers, either wheeled or tracked. The tracked vehicles are usually armoured vehicles specifically designed to carry SAMs. Larger SAMs may be deployed in fixed launchers, but can be towed/re-deployed at will. The smallest of SAMs are capable of being carried and launched by a single person. These types of SAM are also referred to as Man-Portable Air Defence Systems (MANPADS). Soviet MANPADS have been exported around the world and can still be found in many of their former client states. Other nations have developed their own MANPADS.
Ship-based SAMs are in widespread use. Virtually all surface warships can be armed with SAMs (see list below). In fact, naval SAMs are a necessity for all front-line surface warships. Some warship types specialise in anti-air warfare e.g. Ticonderoga-class cruisers equipped with the Aegis combat system or Kirov class cruisers with the S-300PMU Favorite missile system.

Targets for non-ManPAD SAMs will usually be acquired by air-search radar, then tracked before/while a SAM is "locked-on" and then fired. Potential targets, if they are military aircraft, will be identified as friend or foe before being engaged.

Development of surface-to-air missiles began in Nazi Germany (hard pressed by Allied air superiority) during late World War II with missiles such as the Wasserfall though no working system was deployed before the war's end.

See also

• List of surface-to-air missiles

• Missile guidance

• List of NATO reporting names for surface-to-air missiles

• Anti-aircraft warfare

• Man-portable air-defence system

• SEAD, Suppression of Enemy Air Defenses, the mission of finding and destroying SAM and AA gun installations. The SEAD mission in the United States Air Force is designated “Wild Weasel”.