In Whyte notation, a 2-4-0 is a railroad steam locomotive that has two leading wheels followed by two coupled driving wheels, with no trailing wheels.

Other equivalent classifications are:
UIC classification: 1B (also known as German classification and Italian classification)
French classification: 120
Turkish classification: 23
Swiss classification: 2/3

In the UK several classes of 2-4-0s were designed by James Holden for the Great Eastern Railway, including the T19, the "Humpty dumpty" and the T26.

In addition, a class of this type hauled the first Orient Express from Paris to Munich — a notable achievement for a small locomotive.

The March Engineering racing car manufacturer also applied the designation to a six-wheeled Formula One racing car design from 1977, the March 2-4-0.