A nail gun, nailgun or nailer is a form of hammer used to drive nails into wood or other materials. It is usually driven by compressed air (pneumatic), electromagnetism, highly flammable gases such as butane or propane, or, for powder-actuated tools, a small explosive charge. Nail guns have in many ways replaced hammers as tools of choice among builders.

The nail gun was designed by Morris Pynoos, a civil engineer by training, for his work on Howard Hughes' Hughes H-4 Hercules (known as the Spruce Goose). The wooden fuselage was nailed together and glued, and then the nails were removed.

The first nail gun used air pressure and was introduced to the market in 1950 to speed the construction of housing floor sheathing and sub-floors. With the original nail gun, the operator used it while standing and could nail 40-60 nails a minute. It had a capacity of 400-600 nails.