Has anyone ever won an academy award for the same character?

Four actors have been nominated for Best Actor more than once for the same character:

Bing Crosby as Father O'Malley in "Going My Way" which gave him his Oscar and "The Bells of St. Mary's" that gave him a nomination a year later.

Peter O'Toole as King Henry II in "Becket" and "The Lion in Winter"

Paul Newman as "Fast Eddie" Felson in "The Hustler" and "The Color of Money" for which he won the Academy Award.

Cate Blanchett is the only actress to be nominated twice for the same role (Queen Elizabeth I), first for 1998's "Elizabeth" and then again for 2007's "Elizabeth: The Golden Age."

Al Pacino was nominated in 1975 for a role for which he had previously been nominated for Best Supporting Actor, Michael Corleone, in The Godfather Part II.

It's hard to say. The Academy definitely doesn't have a history of favoring films based on comics. Despite the popularity (both with audiences and critics) of Batman Begins and the Spider-Man and X-Men trilogies, none were nominated for, say, Best Picture, Best Director, or Best Actor. But this is a unique situation. Heath Ledger was a popular young actor with a previous nomination under his belt and his death was incredibly surprising and tragic. And early word is his performance as the Joker is terrifying and creative. So I wouldn't be TOO surprised if the Academy overcame their anti-comic/fantasy/science fiction bias and gave him a nomination. I wonder though - would it be for Best Actor or Best Supporting Actor? Isn't Christian Bale ultimately the star of the film and franchise? I doubt he will win though. They will see the nomination itself as a sign of respect and probably give the win to an actor in a more serious dramatic film - perhaps Leonardo DiCaprio for Revolutionary Road (he's so overdue an Academy Award win) or Benicio del Toro for the epic Che Guevara project. ***TO THE PERSON BELOW: How can you judge his performance? You've only seen bits and pieces in the trailers and TV spots and fans have had nothing but praise. You talk as if you already saw the movie, which doesn't open until July 18th.***

No. Very few actors have even won more than one Academy Award. It's incredibly unlikely that someone would get recognized twice for playing the same person, because the whole point of the award is transforming yourself into someone different.

No, but Paul Newman was nominated for playing the same character twice. He was nominated for his role as "Fast" Eddie Felson in The Hustler (1961) and in The Color of Money (1986). He won for The Color of Money.

Marlon Brando and Robert DeNiro both won for playing Vito Corleone.