The Cleethorpes trolleybus system once served the holiday resort of Cleethorpes, in Lincolnshire, England. Opened on 18 July 1937, it replaced part of the Great Grimsby Street Tramways, a tramway that had served both Cleethorpes and the neighbouring seaport of Grimsby. It was closed on 4 June 1960.

Cleethorpes is a seaside town on the estuary of the Humber in North East Lincolnshire, Lincolnshire, England with a population of 38,372 in 2020. It has been permanently occupied since the 6th century, with fishing as its original industry, then developing into a resort in the 19th century. Before becoming a unified town, Cleethorpes was made up of the three small villages of Itterby, Oole and Thrunscoe.