A firearm magazine loader. The loader includes a body having a linear projection extending from the top of the loader for holding rounds of ammunition and an optional plunger for pushing the rounds into a magazine. The loader accommodates and centers a wide variety of magazines due to a self-centering mechanism incorporated into the body. An angled feed channel pivots the rounds into position to slide under the feed lips of a magazine to significantly reduce the insertion force required and allow a double stack magazine to be quickly filled to capacity with minimal effort.