The Birmingham trolleybus system once served the city of Birmingham, in the West Midlands region of England. Opened on , it supplemented Birmingham's original tramway network.
By the standards of the various now-defunct trolleybus systems in the United Kingdom, the Birmingham system was a medium-sized one, even though Birmingham was then, and still is, the most populous British city outside London. With a total of only five routes, and a maximum fleet of 78 trolleybuses, it was closed relatively early, on .
None of the former Birmingham trolleybuses is recorded as having survived.