Thornton, 41, is currently skating with HC Davos in the Swiss National League in preparation of the 2020-21 NHL season. His contract with the Leafs is for $700,000.
A native of London, Ontario, Thornton has been one of the most dominant offensive players of the past two decades in the NHL. Since entering the league in 1997-98, after being drafted first overall by Boston in 1997, he amassed 1,509 points in 1,636 games with the Sharks and Bruins -- most among active players. He's 14th in career points and seventh in career assists (1,089). He won the NHL scoring title in 2005-06 along with MVP honors.
He had 31 points in 70 games for the Sharks last season, skating a career low 15:30 per game on average. Thornton had signed a series of one-year contracts with the Sharks, and was reportedly frustrated when the team failed to move him to a contender at last season's trade deadline, given that San Jose was going to miss the playoffs for the first time in five seasons.
Now, he'll have a chance to chase his first Stanley Cup with his hometown team.