TORONTO — Two years removed from toiling in the NBA's G League, Pascal Siakam led the Toronto Raptors to an historic victory on Thursday.

The 25-year-old from Cameroon scored 32 points to lift the Raptors to a thrilling 118-109 victory over defending champion Golden State Warriors, giving Toronto a 1-0 lead in its NBA Finals debut.

Kawhi Leonard had 23 points on 5-for-14 shooting against a swarming, smothering Warriors defence.

Marc Gasol, who was acquired at February's trade deadline to help the Raptors' playoff push, had 20 points and seven rebounds before fouling out of the game with 1:14 to play.

Kyle Lowry finished with nine assists but just seven points. Fred VanVleet had 15 points, while Danny Green shrugged off the shooting slump that plagued him in the conference finals to finish with 11.

Game 2 is Sunday before the Finals shift to Oakland, Calif., for Games 3 and 4.

After Game 1, Raptors coach Nick Nurse recalled how Siakam came to the gym after the team was eliminated in the playoffs two years ago and said "Listen, I need to learn how to shoot."

"He was extremely hard working," Nurse said. "Just super, super committed to finding a place in this league and improving his game."

Stephen Curry had 34 points to lead the Warriors, who are making their fifth consecutive Finals appearance, and are by far the more experienced squad, boasting a combined 140 Finals games between them, compared to Toronto's 38.

Warriors coach Steve Kerr was full of praise for the Raptors.

"They played a great game, they deserved to win," Kerr said. "We've got to play better if we're going to beat them."

Kerr had talked about the magnitude of the Finals compared to the first three rounds of the playoffs.

"It's just different," he said in his pre-game press conference. "Everything about it feels different. It completely takes you out of your comfort zone."

The Raptors though seemed thoroughly comfortable in the moment. While the Warriors hadn't played in 10 days after sweeping Portland in the west finals, Toronto rode the momentum of four straight wins against Milwaukee in the Eastern finals, cobbling together a 10-point lead in the first half, and stretching it to 12 by the third quarter. The Raptors led 88-81 with one quarter left.

Golden State pulled to within three early in the fourth. But when Lowry hurled a long pass to Siakam for an easy basket, it put Toronto up by seven. Green's three-pointer with 7:31 to play made it a 12-point game, and brought the delighted capacity crowd of 19,983 fans, including golfer Bubba Watson, out of their seats.

The Raptors matched the Warriors virtually shot for shot down the stretch, and when VanVeet's long jumper circled around the rim, as the crowd held its collective breath, before dropping with 3:21 to play, Toronto went back up by a dozen.

Golden State would pull to within seven with just over a minute to play, but the win was already well in hand. Lowry drilled an icing-on-the-cake three with 30 seconds to play and the crowed erupted.

Drake, who's been a lightning rod in the post-season for his on-court antics, came dressed in a No. 30 Dell Curry jersey. Dell (Steph Curry's dad) played for the Raptors from 1999 to 2002.

Siakam's points were the most by a player 25 or younger in their Finals debut since 2012 (Kevin Durant, 36 points for Oklahoma City).

It was a night of firsts. The first NBA Finals for the Raptors, a story 24 years in the writing. It's was the first NBA Finals game held outside the United States, and so the first time "O Canada" was sung at an NBA Finals — performed by The Tenors. The celebratory Scotiabank Arena fans were so loud, they entirely drowned out the Tenors by the anthem's final few words.

Jordan Smith, winner of Season 9 of "The Voice," sang the U.S. national anthem.

According to several online ticket agencies, it was the most expensive Game 1 in NBA history. The average resale price was about US$1,360, almost double the average price of last season's Game 1 between the Warriors and Cleveland Cavaliers.

Every logo in Raptors history was splashed across the giveaway T-shirts.

Lowry said it was the loudest he had ever heard the building.

"It was pretty crazy in there tonight," he said. "We've got the best fans in the NBA and they're just showing it every single night."

Six Raptors scored in a first quarter that saw Toronto race out to a seven-point lead. A running dunk by Thompson capped an 8-0 Warriors run that had the visitors up by a point. Toronto replied with a 7-0 run and led 25-21 heading into the second.

The Raptors shot 65 per cent in the second quarter, and when Green connected on a three-pointer with 11 seconds left, the bucket sent Toronto into the halftime break with a 59-49 lead as chants of "Dan-ny!" rained down from the crowd.

Outside the arena, thousands of festive fans packed Jurassic Park, many of whom had been there at dawn to line up.

Raptors alumni were honoured at centre-court during a timeout, including the team's first general manager Isiah Thomas, plus Muggsy Bogues, Charles Oakley, Jerome (JYD) Williams, Dell Curry, Tracy McGrady, Morris Peterson, Chris Bosh, and a Year 1 Raptor Damon Stoudamire.

Rapper Kardinal Offishall performed "The Anthem," his ode to Toronto, during a timeout. Rapper ASAP Ferg performed at halftime.

In his pre-game press conference, NBA commissioner Adam Silver talked about the Finals being a full-circle moment. The first NBA game was played between the Toronto Huskies and New York Knickerbockers at Maple Leaf Gardens in 1946.

The presence of a non-American team, he said, might be felt on a global scale.

"Symbolically having our first Finals outside the United States maybe has a big impact on countries that follow the NBA but don't have teams," Silver said. "This clearly is a marker of sorts that here we are 2019, our Game 1 of the Finals taking place in Toronto, Canada. That will be a milestone.

"It's come full circle in terms of basketball being invented by a Canadian."