Barry Graham Purkis, more commonly known as Thunderstick (born 7 December 1954), is an English drummer who wore various masks and used to perform on-stage closed in a cage. He was in the popular cult-band Samson, with whom his name is most associated.

In 1979 he developed his persona modelled on horror icons such as The Rocky Horror Show, Dr. Phibes and the old Hammer horror films, alternatively wearing black and white make-up, an old man/schoolteacher mask, a black cotton mask and his trademarked rhinestone covered mirrorball mask.. He played inside a cage, including during a brief Samson reunion in 2000. With Samson he enjoyed a certain degree of success, especially when their album Head On was released in 1980 and reached No. 34 in the UK charts. The following single Riding With The Angels, from the album Shock Tactics, charted in the UK at No. 54.

In a rare occurrence his face was seen when he performed the main-role in the b-movie Biceps of Steel, featuring his band at the time Samson. In the film his then brother-in-law Ben K. Reeves performed as Thunderstick in his stead, only for the shots where Purkis and Thunderstick were set to appear at the same time.

In the June 2005 issue of Classic Rock Magazine, Thunderstick was listed as no. 36 in the "50 Greatest Drummers in Rock" feature.