Who won the Academy Award for Best Actor of 1943?

James Cagney for Yankee Doodle Dandy.
The Academy Award winner for Best Actor in 1942 was James Cagney in the movie "Yankee Doodle Dandy"
James Cagney won the 1942 Oscar for Best Actor for his performance as song-and-dance man George M. Cohan in "Yankee Doodle Dandy."