The Teesside trolleybus system once served the conurbation of Teesside, in the North East of England. Opened on 8 November 1919, it was unusual in being a completely new system that was not replacing any previously operating tramway network. By the standards of the various now defunct trolleybus systems in the United Kingdom, the Teesside system was a small one, with a total of three routes, and a maximum fleet of only 21 trolleybuses. However, it was unusually long-lasting, as it did not close until 18 April 1971, and was therefore the penultimate system in the UK to do so.