A locking adjustable cheek rest comprising an upper U-shaped portion and a lower portion located on the stock of a rifle or other firearm. The U-shaped portion is biased against the lower portion, such that the walls of the U-shaped upper portion press against the lower portion, thereby locking the upper portion in position. A first release and a second release are depressed to release the bias and enable the upper portion to be raised and lowered relative to the lower portion. Interlocking mechanisms located on the upper and lower portions facilitate locking of the cheek rest in a position determined by the user.