An atlatl (/ˈɑːt.lɑːtəl/ or /ˈæt.lætəl/; Classical Nahuatl: ahtlatl [ˈaʔtɬatɬ]) or spear-thrower is a tool that uses leverage to achieve greater velocity in dart-throwing.

It consists of a shaft with a cup or a spur at the end that supports and propels the butt of the dart. The atlatl is held in one hand, gripped near the end farthest from the cup. The dart is thrown by the action of the upper arm and wrist, using the atlatl as a low-mass, fast-moving extension of the throwing arm. The atlatl acts as a lever that trades force for speed (the inverse of "leverage" as the term is commonly used).

Common ball throwers (molded plastic shafts used for throwing tennis balls for dogs to fetch) use the same principle.

A traditional atlatl is a long-range weapon and can readily impart to a projectile speeds of over 150 km/h (93 mph).

Atlatl designs may include improvements such as thong loops to fit the fingers, the use of flexible shafts, stone balance weights, and thinner, highly flexible darts for added power and range. Darts resemble large arrows or thin spears and are typically from 1.2 to 2.7 m (4' to 9') in length and 9 to 16 mm (3/8" to 5/8") in diameter.