James Stewart 'Jimmy' Bain (born 19 December 1947) is a Scottish bassist most famous for playing in the bands Rainbow and Dio with Ronnie James Dio， He has worked with Thin Lizzy frontman Phil Lynott, co-writing on his solo albums.

Bain was born in Newtonmore, Highland, in Scotland. Jimmy Bain played in several provincial amateur bands as a young teen. Bain's parents and younger brothers relocated to Vancouver, Canada. By this point Bain was playing professionally in Street Noise. However he did join his family for a brief stay in Canada. Before returning to Scotland getting his band Harlot and then hitting the London music scene, Bain joined Harlot in early 1974, after turning down a job with The Babys.