Movies
Penn was the marginal bookies favourite over Bill Murray for Lost In Translation.
"If there's one thing that actors know it's that there is no such thing as a best actor," said Penn. "That's proven by the other nominees here and those who weren't nominated - we know how great all of you are.
"I really thank Clint Eastwood professionally and humanly for coming into my life, the great great cast I had to work with, my friends."
Johnny Depp had been the favourite with Digital Spy readers, chosen by 49% of voters against 36% for Murray and just 5% for Penn.
More: Movies, Oscars 2004
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At the Movies
John Williams's top 10 movie scoresAs John Williams celebrates his 80th birthday, we take a look at his 10 best movie scores.
Movies Interviews
Daniel Radcliffe talks 'Woman in Black'The actor talks to Digital Spy about his first post-Potter outing.
Box Office Charts
'Chronicle' leads UK box officeSuperhero drama Chronicle leads the UK box office ahead of Journey 2.
