Robert Thomas Powell (/ˈpaʊəl/ POW-əl; born 1 June 1944) is an English actor who is known for the title roles in Mahler (1974) and Jesus of Nazareth (1977), and for his portrayal of secret agent Richard Hannay in The Thirty Nine Steps (1978) and its subsequent spinoff television series. Other major screen roles have included Tobias "Toby" Wren in the BBC science-fiction programme Doomwatch (1970), David Briggs in the sitcom The Detectives (1993–1997) with Jasper Carrott, and Mark Williams in the medical drama Holby City (2005–2011).

Powell's distinctive voice has become well known as a narrator of documentaries, especially those concerning the Second World War, including World War II in HD Colour, Hitler's Bodyguard, The Story of the Third Reich and Secrets of World War II.

Powell was nominated for a Best Actor BAFTA TV Award for Jesus of Nazareth in 1978 and won a Best Actor award at the Venice Film Festival for his performance in the film Imperative in 1982.

Powell was born in Salford, Lancashire, the son of Kathleen (née Davis) and John Wilson Powell. He was educated at Manchester Grammar School (which was then a direct grant grammar school), and studied law at the University of Manchester. He has an elder brother, Henry (Harry).

Powell began acting at school, playing the title role in Shakespeare's King Lear. He also appeared as a teenager in The Adventures of Samuel Poppleton on BBC Radio Children's Hour from the North of England in Manchester, where he came under the guidance of producer Trevor Hill, as detailed in Hill's autobiography, Over the Airwaves. He secured a post at a repertory theatre in Stoke-on-Trent. His first film part was in Robbery (1967), which starred Stanley Baker and was about the Great Train Robbery, in which he played the second man or locomotive driver's assistant. He had a small role in the original film version of The Italian Job (1969) playing one of the gang, but had to wait a few years for his first success, playing scientist Toby Wren in the BBC's science fiction series Doomwatch in 1970.

Having been killed off in Doomwatch right at the end of Series One in a bomb explosion, at his request, Powell became a pin-up and a household name, following up with starring roles in several BBC serials, including television adaptations of the novels Sentimental Education (1970) and Jude the Obscure (1971). In 1972–1973 he portrayed Charles Rolls in the miniseries The Edwardians. He starred in 1973 in the first episode of the British series Thriller. He also appeared in the 1975 series Looking for Clancy, based on the Frederic Mullally novel Clancy.

For several years Powell continued as a television regular, with occasional forays into film, as the Austrian composer Gustav Mahler in the Ken Russell biopic Mahler (1974) and Captain Walker in Russell's film version of Tommy (1975). His role in Tommy had few lines, speaking only during the overture with Ann-Margret, he is primarily seen through the mind of his son as played by Barry Winch (Young Tommy) and Roger Daltrey.

Powell then played the title role in Jesus of Nazareth (1977) following a successful second audition with Franco Zeffirelli. The four-part television film had an all-star cast, including Laurence Olivier as Nicodemus, Ernest Borgnine as the Roman Centurion, Stacy Keach as Barabbas, Christopher Plummer as Herod Antipas, Michael York as John the Baptist, Ian McShane as Judas Iscariot, Rod Steiger as Pontius Pilate and James Mason as Joseph of Arimathea. For this role, Powell was nominated for a BAFTA award, and collected the TVTimes Best Actor award for the same performance. His completist performance is frequently considered one of the best portrayals of Christ.