Samuel Barnett (born April 25, 1980) is an English actor. He has performed on stage, film, television and radio, and achieved recognition for his work on the stage and film versions of The History Boys by Alan Bennett. His television performances include roles in the BBC comedy Twenty Twelve and in the Showtime drama Penny Dreadful. He played the lead role of Dirk Gently in the 2016 BBC America adaptation of the Dirk Gently's Holistic Detective Agency book series by Douglas Adams.
Barnett was born in Whitby in North Yorkshire, England. He started performing at an early age before moving to London to study acting at LAMDA. Barnett is one of five children. Barnett's father is of Polish Jewish descent, whereas his mother is of Quaker background.
Barnett appeared in the original London stage production of Alan Bennett's 2004 play The History Boys, as well as in the New York, Sydney, Wellington and Hong Kong productions and radio and film versions of the play. He had been involved in The History Boys from its very first reading.