The Sydney ruckman from Victoria became the first Canadian to play in an Aussie Rules Football grand final, and was among his team's best players.
The Swans kicked the final four goals of the match to respond to a furious Hawthorn comeback and beat the Hawks 14.7 (91) to 11.15 (81) before 99,683 fans at the Melbourne Cricket Ground.
Pyke, a six-foot-four former Canadian rugby international, had an outstanding 16 touches, six marks and 29 hitouts in the match, and was entrusted with being his team's key big man in the nerve-fraying last quarter after Shane Mumford was substituted.
The Swans, who had just one win and a draw in their previous 15 games at the ground, prevailed in a game of wild momentum swings. Hawthorn led by 19 points early but Sydney kicked six goals to none in the second quarter to go into halftime 16 points in front.
But the Hawks responded with seven of eight goals in the third quarter to take what looked a winning lead, only for the Swans to wrest the game back in the closing stages and claim only their second premiership in 79 years. The Swans relocated from South Melbourne to Sydney in 1982 and won the title in 2005 in a similar nail-biting contest.
The game was played in gusty but dry conditions despite a forecast of hail and rain throughout the match.
Hawthorn midfielder Brad Sewell missed two snaps for goal in the final minutes, the first of which would have levelled the scores and the second which would have given the Hawks the lead had they been accurate.
With Sydney leading by four points, the clinching goal came with 34 seconds left when defender Nick Malceski, who had kicked Sydney's first goal from a near-impossible angle, slotted another snap goal and was besieged by jubilant teammates.
Only four Swans — Adam Goodes, Lewis Roberts-Thomson, Jude Bolton and Ryan O'Keefe — playing on Saturday were part of the club's 2005 title, with Malceski one of another three that played in the 2006 grand final when they lost by one point to West Coast.
Goodes, Sydney's talismanic figure, paraded the AFL trophy around the ground Saturday with his teammates in tow, many stopping to salute the thousands of fans who travelled from Sydney for the final.
"This is the best part of the game," Goodes said of the celebration. "You work so hard to get here, doing this is why you play football."
Sydney coach John Longmire said Goodes ruptured the posterior cruciate ligament in his left knee early in the second quarter when the Swans began their comeback.
The co-captain hung on to kick the game's second-to-last goal.
"I asked him a couple of times during the course of the game 'Are you all right?' He didn't even flinch, it was 'Don't worry about me,'" Longmire said. "To have a knee that was essentially gone and hang on like he did was a sensational effort."
Josh Kennedy, traded from Hawthorn to Sydney in 2010, was among five Swans to kick two goals and continue an AFL premiership tradition. His grandfather, John Kennedy Sr., coached the club to their first premiership in 1961 and subsequent league titles in 1971 and 1976. Josh Kennedy's father, John Jr., won four premierships as a player with the Hawks in 1983, 1986, 1988 and 1989.