The Grimsby trolleybus system once served the seaport of Grimsby, in Lincolnshire, England. Opened on 3 October 1926, it gradually replaced part of the Great Grimsby Street Tramways, a tramway that had served both Grimsby and the neighbouring holiday resort of Cleethorpes. It was closed on 4 June 1960. By the standards of the various now defunct trolleybus systems in the United Kingdom, the Grimsby system was a small one, with a total of only two routes, and a maximum fleet of just 19 trolleybuses.