Carlyle, let go by Anaheim earlier in the season, will be behind the bench for Saturday's game in Montreal.
The move comes just months after GM Brian Burke gave Wilson a one-year contract extension in late December.
"This was not an easy decision for me to make," Burke said in a statement. "I want to thank Ron for all of his hard work and dedication to our organization over the past four seasons."
The Leafs, solidly in the top eight in the East for the first two-thirds of the season, have won just once in their last 11 games -- the 1-9-1 slide has dropped them five points out of the final postseason berth with a 29-28-7 record. Chants of "Fire Wilson!" echoed through Air Canada Centre when the Maple Leafs lost 5-3 to the Florida Panthers on Tuesday night. They lost 5-4 at Chicago the following night after blowing a 3-1 lead.
Toronto has not made the Stanley Cup Playoffs since 2004, the longest postseason drought in franchise history and the second-longest active non-playoff streak in the League.
Carlyle was the coach and Burke the general manager when the Anaheim Ducks won the Stanley Cup in 2007. The 55-year-old former defenseman had a 273-182-61 mark in six-plus seasons behind the bench in Anaheim and led the Ducks to five playoff appearances.
Carlyle becomes the 29th coach in Toronto history and the 16th to have played for the Maple Leafs and then taken the reins as coach. The former Norris Trophy winner with the Pittsburgh Penguins played 94 games on the blue line for the Leafs from 1976-78 and had two goals and 16 assists.
"Although it’s always tough to see a coaching change, we are certainly happy for Randy. It was simply a matter of time before he had another opportunity to be a head coach in this League," Ducks GM Bob Murray said. "He’s a great coach, and we wish him the best in Toronto."
The Leafs hired Wilson in 2008, and they went 34-35-13 mark in his Maple Leafs debut, finishing 12th in the Eastern Conference. They were 30-38-14 and finished last in the Conference in 2009-10. Wilson had his first winning season with the Maple Leafs in '10-11, going 37-34-11, but that was only good enough for 10th in the East.
Wilson began his NHL coaching career in Anaheim and has also coached at Washington and San Jose. In 1,361 games, he has a record of 634-546-101-87, including 130-135-45 with the Leafs.