A multiple caliber firearm magazine loader. The loader provides two main features. First, the loader provides the capability to pick up rounds of ammunition in a wide variety of calibers. Second, the loader has a body that accommodates a large number of magazines with a variety of form factors and dimensions designed to work with a diverse collection of firearms. The body has multiple alignment features that align the feed opening of magazines with the rail of the loader in order to receive rounds of ammunition as they are pushed downward along the rail.