Brian Cook is an American bass guitarist currently in the bands Russian Circles and Sumac. He was also previously a full-time member of Botch, These Arms Are Snakes and Roy, and also a session musician for Mouth of the Architect. Cook is also a freelance journalist and has published a book titled The Second Chair is Meant for You. He is openly gay.

Russian Circles is an American post-metal band based in Chicago, Illinois. The band was originally formed by childhood friends Mike Sullivan and Dave Turncrantz after their previous musical projects dissolved. After parting ways with their original bass player Colin DeKuiper in 2007, the trio was rounded out by Brian Cook. The band has gained widespread recognition based on a series of critically acclaimed albums and extensive international touring. Their name is taken from a drill exercise used in ice hockey, a sport Sullivan and Turncrantz grew up playing in their original hometown of St. Louis.