The Caledonian Railway 191 Class were 4-6-0 passenger engines designed by William Pickersgill and built in 1922 by the North British Locomotive Company. The class was intended for use on the Callander and Oban line, to augment the 55 Class 4-6-0s and replace elderly 179 Class 4-4-0s, and they were thus known as the New Oban Bogies, however, they were also used on other Caledonian lines.