4-8-4

Under the Whyte notation for the classification of steam locomotives, 4-8-4 represents the wheel arrangement of four leading wheels on two axles, usually in a leading truck, eight powered and coupled driving wheels on four axles, and four trailing wheels on two axles, usually in a trailing truck. The type was first used by the Northern Pacific Railway and is consequently most commonly known as a Northern.

Other equivalent classifications are:

• UIC classification: 2D2 (also known as German classification and Italian classification)
• French classification: 242 (also known as Spanish classification)
• Turkish classification: 48
• Swiss classification: 4/8
• Russian classification: 2-4-2