James Broadbent (born 24 May 1949) is an English actor.

Born in Lincolnshire to parents who were both amateur actors, he was educated at Leighton Park School, a Quaker school in Reading, and briefly attended art college before transferring to the London Academy of Music and Dramatic Art. He graduated in 1972. His early stage work included appearances as Patrick Barlow's assistant in the mock National Theatre of Brent.

He won the Academy Award for Best Supporting Actor for Iris and the BAFTA Award for Best Actor in a Supporting Role for Moulin Rouge!, both in 2001, and the British Academy Television Award for Best Actor and Golden Globe Award for Best Actor – Miniseries or Television Film for his portrayal of penal reformer Lord Longford in the Channel 4 drama Longford in 2006. He portrayed Professor Horace Slughorn in the Harry Potter series. In 2017, Broadbent joined the cast of the HBO series Game of Thrones, playing the role of Archmaester Ebrose.