Ian McDiarmid Ian McDiarmid ( born August 11 , 1944 ) portrayed Darth Sidious in the " Star Wars " films . He appears in every film of the prequel trilogy , as well as in " " . He did not play the Emperor in the original release of " " , but was edited in for the DVD release of the original trilogy . He has the distinction of being one of the few actors from the original trilogy to reprise the role of a Human character in the prequel trilogy . McDiarmid also worked with George Lucas on the 1992 television series " " , in which McDiarmid portrayed Professor Levi in the episode " Paris , October 1916 . " He has also had a distinguished career in British theatre , working as Associate Artistic Director for the Royal Exchange Theatre , Manchester ( 1986 - 1989 ) , joint Artistic Director at London ' s Almedia Theatre ( 1990 - 2002 ) and as a Board Member of the National Theatre of Scotland . Recent and upcoming projects include a return to the role of Teddy in Brian Friel ' s " Faith Healer " ( for which he won a Tony award ) and in the world premiere of Robert Holman ' s " Jonah & Otto " , which marks his return to the Royal Exchange . Biography . Ian McDiarmid was born in , , in 1940s # 19441944 . He became a theatre aficionado when he was five years old , when his father took him to see an act by the name of Tommy Morgan in a theatre located in . In 2001 he stated , " " It sort of fascinated me , and it also scared me . All those lights , all that make - up . I said to myself , ' I don ' t know what this is , but I want it . " " However , fearing his father ' s disapproval , McDiarmid attended the , where he received an in psychology . Soon after , he decided to pursue a career in the theatre instead , and took acting training courses at the in . In 1968 , McDiarmid received a gold medal for his work . This would later prove to be the first of many recognitions given to him for his work in the theatre . 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 in . 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 . His directing work with the Almeida Theatre includes " Scenes from an Execution " with Glenda Jackson and " Lulu " with Joanne Whaley . McDiarmid himself portrayed many roles , including Goya in the opera work " Terrible Mouth " , the title role in " Volpone " and " The Jew of Malla " — which was performed at the Almeida and on tour in 1999 . In 1982 , he played Harry Hackamore , a Howard Hughes - type character , in the play " Seduced " , by Sam Shepard . This showed his ability to convincingly play , in close - up , a character much older than himself . This is what attracted the attention of George Lucas and Richard Marquand , who decided that he could play the Emperor in " Return of the Jedi " , which was already in production at the time . Following " Return of the Jedi " , McDiarmid co - starred in the 1989 movie " " , directed by Frank Oz . On October 22 nd , 2008 , McDiarmid suffered a suspected heart attack while on stage performing in " " at the in . The actor suffered dizzy spells during the performance , but finished the show before going to the hospital . After a week ' s recuperation , he returned to the show but , as with much of his personal life — little is known beyond his living alone for much of his time in London — the subject is not one he is willing to dwell on . Many magazines and websites cited McDiarmid as a heroic actor , but he says in " Times Online " that he never even thought that way : " " It was a big house , the pressure was on not to be crap . Very early on I thought , I really should not have eaten that sandwich so quickly , and I was irritated with myself . As the evening went on , I realised it was more than mild irritation , but I wasn ’ t being heroic . When I got off the stage , I said to the stage manager , ' I think I need a doctor ' , and she said , ' my friend ' s a doctor and she ’ s here tonight ’ . So then I surrendered , an ambulance arrived , took me to the hospital , and doctors examined me . " "