0-6-6-0

In Whyte notation, a 0-6-6-0 is a railroad steam locomotive that has two articulated sections, each with six coupled driving wheels, without any leading wheels or trailing wheels.

Other equivalent classifications are:

UIC classification: CC (also known as German classification and Italian classification)

French classification: 030+030

Turkish classification: 33+33

Swiss classification: 3/3+3/3

The first Mallet locomotive built in the United States, Baltimore and Ohio Railroad #2400 (Class O), was of this type.

The only example of this type of engine in the UK was the "Leader". It was originally commissioned by the Southern Railway but it was completed by British Railways in 1949. It was effectively a Meyer locomotive since both sets of drivers were articulated. In UIC classification this would be written C'C'.