Under the Whyte notation for the classification of steam locomotives, 2-10-2 represents the wheel arrangement of two leading wheels on one axle, usually in a leading truck, ten powered and coupled driving wheels on five axles, and two trailing wheels on one axle, usually in a trailing truck. In the United States and elsewhere the 2-10-2 is known as the Santa Fe type, after the Atchison, Topeka and Santa Fe Railway that first used the type in 1903.
Other equivalent classifications are:
- UIC classification: 1E1 (also known as German classification and Italian classification)
- French classification: 151 (also known as Spanish classification)
- Turkish classification: 57
- Swiss classification: 5/7
- Russian classification: 1-5-1