A firearm magazine loader for loading both rounds held by a stripper clip and for loading loose rounds into a magazine comprises, in one aspect, a stick-like body having a lower portion adapted to fit over and attach to an open top end of a magazine and an upper portion for receiving a loaded stripper clip or loose rounds. A tiltable and slideable slider is coupled inseparably to slots in the upper portion and slidable along it. Loading is achieved by using the slider to thrust down the top-most round in the upper portion, causing all other rounds below to be forced sequentially and quickly into the magazine. The loader also includes and unloading flange for unloading rounds from the magazine.