2-10-0

Under the Whyte notation for the classification of steam locomotives, 2-10-0 represents the wheel arrangement of two leading wheels on one axle, ten powered and coupled driving wheels on five axles, and no trailing wheels. This arrangement was often named Decapod, especially in the United States, although this name was sometimes applied to locomotives of 0-10-0 "Ten-Coupled" arrangement, particularly in the United Kingdom. Notable German locomotives of this type include the war locomotives of Class 52.

These locomotives were popular in Europe, particularly in Germany and Russia; British use of the type was confined to the period during and after World War II. In the United States, the 2-10-0 was not widely popular but was a favorite of a small number of railroads which operated mostly in mountainous terrain. Among these was the Erie Railroad, a major Chicago to New York trunk line railroad, and the Pennsylvania Railroad, whose heavily graded routes crossed the Allegheny Mountains.