Ian McDiarmid was born in Tayside, Scotland, in 1944. He studied for an M.A. in Clinical Psychology at The University of St Andrews, but eventually found that his calling was in theatre. He went to the Royal Academy in Glasgow, where he received the prestigious gold medal for his work. He now has a highly successful career as a theatre director, and from 1990 until his retirement in 2001 was Joint Artistic Director of London's Almeida Theatre in Islington. He and his co-director Jonathan Kent revived the Almeida and persuaded many Hollywood stars including Kevin Spacey, Ralph Fiennes and Anna Friel to tread the boards in their humble theatre. They won the coveted London Evening Standard Award in 1998 for their efforts. McDiarmid is also well known for his film and television appearances, and is perhaps most famous for his chilling performance as The Emperor in George Lucas's Star Wars films.
| Movie | Obi-Wan Kenobi: A Jedi's Return | Self - Emperor Palpatine | 2022-09-07 |
| Movie | The Skywalker Legacy | Self | 2020-03-18 |
| Movie | Star Wars: The Rise of Skywalker | Emperor Palpatine | 2019-12-18 |
| Series | Britannia | King Pellenor | 2018-01-18 |
| Movie | The Lost City of Z | Sir George Goldie | 2017-03-15 |
| Movie | Star Wars Rebels: The Siege of Lothal | Emperor Palpatine (voice) | 2015-04-18 |
| Movie | Star Wars: Evolution of the Lightsaber Duel | Self | 2015-12-15 |
| Movie | Star Wars: Greatest Moments | Self | 2015-12-26 |
| Series | 37 Days | Sir Edward Grey | 2014-03-06 |
| Series | Star Wars Rebels | Emperor Palpatine | 2014-10-13 |
| Series | Utopia | Anton | 2013-01-15 |
| Movie | Margaret | Denis Thatcher | 2009-03-26 |
| Movie | The Odds | 2009-10-20 | |
| Series | City of Vice | Henry Fielding | 2008-01-14 |
| Movie | Our Hidden Lives | B. Charles | 2005-10-03 |
| Movie | Star Wars: Episode III - Revenge of the Sith | Chancellor Palpatine / Darth Sidious | 2005-05-17 |
| Movie | Star Wars: A Musical Journey | Host | 2005-05-03 |
| Series | Elizabeth I | Lord Burghley | 2005-09-29 |
| Movie | The Story of Star Wars | Palpatine/The Emperor (archive footage) | 2004-08-18 |
| Series | Charles II: The Power and The Passion | Sir Edward Hyde | 2003-11-16 |
| Movie | Crime and Punishment | Porfiry | 2002-02-12 |
| Movie | Star Wars: Episode II - Attack of the Clones | Chancellor Palpatine | 2002-05-15 |
| Series | Spooks | Unknown | 2002-05-13 |
| Movie | The Beginning: Making Episode I | Self | 2001-10-16 |
| Movie | Sleepy Hollow: Behind the Legend | Self | 2000-05-23 |
| Movie | Great Expectations | Jaggers | 1999-04-12 |
| Series | Great Expectations | Jaggers | 1999-04-12 |
| Movie | Star Wars: Episode I - The Phantom Menace | Senator Palpatine | 1999-05-19 |
| Movie | Sleepy Hollow | Dr. Lancaster | 1999-11-19 |
| Movie | The Adventures of Young Indiana Jones: Demons of Deception | Prof. Levi | 1999-10-31 |
| Movie | All the King's Men | Rev. Pierrepoint Edwards | 1999-11-14 |
| Series | Cold Lazarus | Oliver Morse | 1996-05-26 |
| Series | Karaoke | Oliver Morse | 1996-04-28 |
| Movie | Hillsborough | Doctor Popper, Coroner | 1996-09-11 |
| Movie | Annie: A Royal Adventure | Dr. Eli Eon | 1995-11-18 |
| Movie | Restoration | Ambrose | 1995-12-29 |
| Movie | Heart of Darkness | Doctor | 1993-10-01 |
| Movie | Chernobyl: The Final Warning | Dr. Vatisenko | 1991-04-22 |
| Movie | Dirty Rotten Scoundrels | Arthur | 1988-12-14 |
| Series | Inspector Morse | Unknown | 1987-01-06 |
| Movie | Gorky Park | Professor Andreev | 1983-12-15 |
| Movie | Return of the Jedi | The Emperor | 1983-05-25 |
| Series | The Nation's Health | Dr Vernon Davis | 1983-10-06 |
| Movie | Dragonslayer | Brother Jacopus | 1981-06-26 |
| Movie | The Awakening | Dr. Richter | 1980-07-09 |
| Movie | The Empire Strikes Back | Emperor (Special Edition) | 1980-05-20 |
| Movie | Sir Henry at Rawlinson End | Reg Smeeton | 1980-11-07 |
| Movie | Richard's Things | Burglar | 1980-12-26 |
| Movie | Macbeth | The Porter / Ross | 1979-02-02 |
| Movie | Amazing Stories | Blade | 1976-02-01 |
| Movie | The Likely Lads | Vicar | 1976-02-01 |