In most countries special forces (SF) is a generic term for highly-trained military units that conduct specialized operations such as reconnaissance, unconventional warfare, and counter-terrorism actions. In the United States, the term Special Operations Forces (SOF) is used instead of special forces to refer to the aforementioned units because Special Forces refers to a specific unit, the United States Army Special Forces or "Green Berets".

Some special forces operations, such as counter-terrorism actions, may be carried out domestically under certain circumstances. Special forces units are typically composed of relatively small groups of highly-trained personnel equipped with specialist equipment and armament, operating under principles of self-sufficiency, stealth, speed, and close teamwork. Special forces are sometimes considered a force multiplier, as when they train indigenous forces to fight guerrilla warfare.