The Blackhawks downed the Flyers in six games to win the NHL's top prize for the fourth time in their history.
Chicago was on the verge of celebrating the championship as time wound down in regulation but Scott Hartnell tipped in a shot with 3:59 remaining in the third period to tie it at 3-3 and briefly keep Philadelphia's season alive.
Kane, however, flipped a wrist shot from a sharp angle past a screened Michael Leighton soon after the overtime had begun, touching off a victory celebration by one of the NHL's original six franchises.
The teams battled to a 1-1 tie through the opening period but Philadelphia grabbed its only lead of the game 8 minutes into the second on a goal from Danny Briere -- his 12th of the playoffs.
Chicago then tied it on Patrick Sharp's wrist shot midway through the period and took a 3-2 lead on Andrew Ladd's tip-in with 2:17 to go in the stanza.
Antti Niemi, in his first trip to the playoffs, became a Stanley Cup winning goaltender by making 21 saves. He was in goal for all 16 of Chicago's post-season triumphs this season.
Leighton, a hero in Philadelphia's comeback series victory over Boston in the Eastern Conference semifinals, struggled in Game 6 of the Stanley Cup Finals, gave up four goals on 41 shots.
The Conn Smythe Trophy as the post-season MVP went to Chicago captain Jonathan Toews. He had only three assists in the final series, but in 22 playoff games he had seven goals and 22 assists.