Advanced Combat Optical Gunsights (abbreviated ACOG) are a series of advanced telescopic combat sights manufactured by Trijicon. The ACOG is designed to be used on the AR-15 and M4 carbine rifle, but Trijicon has developed ACOG scopes for many other firearms. ACOG Models provide magnification levels up to 8X.

Unlike many reflex gun sights, the Trijicon ACOG does not require battery power. The superimposed recital sight, available in a variety of patterns and colors, is illuminated by an external fiber optic light-gathering rail when available light is plentiful and by an internal tritium lamp during low-light use.