The Great Western Railway 3700 Class, or City Class, locomotives were a series of twenty 4-4-0 steam locomotives, designed for hauling express passenger trains.

In September 1902 a member of the Atbara Class, no. 3405 Mauritius, was reboilered with a tapered domeless boiler and Belpaire firebox becoming the prototype for the City Class. In March 1903 the first of the City Class, no. 3433 City of Bath, was completed. Another nine locomotives were completed in May 1903. Between February 1907 and December 1908 nine more Atbaras were rebuilt and incorporated into the City Class

The most famous locomotive in the class, 3440 City of Truro (later renumbered 3717), is reputedly the first steam locomotive to travel in excess of 100 mph, on 9 May 1904. It was the 2000th locomotive to be built at Swindon, leaving the works in April 1903.

Historically significant because of its famed 1904 run, City of Truro was a prime candidate for preservation, whereas the rest of the class of 20 locomotives were scrapped.