"I can't wait to get to work with this ridiculously talented 2.5 team and I believe we can fill the stage with laughter that will echo in viewers' homes," Kutcher said in the statement. "I can't replace Charlie Sheen but I'm going to work my ass off to entertain the hell out of people."
Sheen's well-publicized problems and his very public rants got him fired from "Two and a Half Men."
"We are so lucky to have someone as talented, joyful and just plain remarkable as Ashton joining our family," said the show's creator and executive producer Chuck Lorre.
The show is getting a transfusion, and when the deal is done, Kutcher is expected to bring new blood to the show's ninth season.
"Both CBS and the studio involved, Warner Bros., had to do their damnedest to make sure they had someone to fill Sheen's shoes," said Andrew Wallenstein, "Daily Variety" TV editor. "After all, this is a billion-dollar juggernaut of a show, and the show must go on."
There are reports that the 33-year-old Kutcher could be paid about $1 million per episode.
These days, Kutcher has been making movies, but television made him a star, with the success of "That '70s Show" and "Punk'd."
On Wednesday, the man with millions of Twitter followers tweeted, "What's the square root of 6.25?" The answer is 2-1/2.