HAG is a Swiss maker of model trains. The company was founded by Hugo and Alwin Gahler on 1 April 1944 in St. Gallen, Switzerland.
The Gahler brothers originally manufactured model trains in O scale but due to competition, particularly by MarklinH0 scale, began the transition to H0 in 1954 with their final O scale set being manufactured in 1957.
Today HAG manufactures die-cast metal model trains and is the primary manufacturer of HO scale Swiss model trains. Models are available in both two-rail DC and Märklin-compatible three-rail AC.