The Firefly was a class of broad gauge 2-2-2 steam locomotives used for passenger services on the Great Western Railway. The class was introduced into service between March 1840 and December 1842, and withdrawn between December 1863 and July 1879. Following the success of the Star class locomotives introduced to the Great Western Railway by Daniel Gooch, Gooch set to work to develop a new class based on North Star, but with larger boilers.