The M18 Hellcat (officially designated the 76mm Gun Motor Carriage M18 or M18 GMC for short) was an American tank destroyer of World War II, used in the Italian, European, and Pacific theatres, and in the Korean War.

It was the fastest armored vehicle in the American defense inventory of the 20th century. The speed was attained by keeping armor to a minimum, no more than one inch thick and roofless, open-top turrets (a standard design feature for all American fully tracked tank destroyers of World War II) and by powering the relatively small vehicle with a radial engine originally designed for aircraft usage.

The Hellcat, along with the M4 Sherman-based M10 tank destroyer and the highly effective, 90mm gun-armed M36 tank destroyer, provided American and Allied forces with a respectable mobile anti-tank capability against the newer German armored types.