LAS VEGAS -- The expansion Vegas Golden Knights will head into 2018 with a three-point lead in the Pacific Division after defeating the Toronto Maple Leafs 6-3 on Sunday afternoon at T-Mobile Arena.

Center William Karlsson scored his first career hat trick and the first in team history and Pierre-Edouard Bellemare, Erik Haula and Jonathan Marchessault also scored. Goalie Malcolm Subban stopped 19 of 22 shots for Vegas (26-9-2), which added to its Pacific Division lead over the idle Los Angeles Kings (23-11-5).

Vegas extended its winning streak to seven games, longest in NHL history for a team in its inaugural season. The Golden Knights also improved to 16-2-1 at T-Mobile Arena and are 11-0-1 in their last 12 games, not having lost a contest in regulation since falling at Atlantic Division leading Winnipeg, 7-4, on Dec. 1.

"Obviously, this streak is unbelievable," Vegas coach Gerard Gallant said. "The guys are playing well, they're playing great hockey every night, and they're competing. We've got points in 12 straight games. You just keep working hard and battling hard, we're getting some puck luck and we're playing good hockey."

Auston Matthews scored two goals and Patrick Marleau added one for Toronto. Frederik Andersen finished with 25 saves in net for the Maple Leafs (23-15-2).

Vegas bolted to a 3-0 lead in the first period. Bellemare notched his fourth goal of the season with a backhand under the glove of Andersen off a pass from Alex Tuch just 2:24 into the game.

Karlsson made it 2-0 at 4:17 with a one-timer from the right circle off a pass from Reilly Smith to finish a two-on-one break.

Haula scored his 14th goal of the season when he picked up the puck at center ice and then fired a wrist shot that defenseman Ron Hainsey appeared to screen Andersen on.

"We knew they were going to come out strong and fast and they did," Marleau said. "It was a matter of us not getting the puck in and getting our forecheck going. Once they start rolling it makes it that much more difficult to get things going the other way."

Marleau scored his 15th goal of the season early in the second period to make it 3-1 when he took a pass from right wing Connor Brown in front of the net and spun around and slid the puck inside the left post.

Karlsson answered at 8:26 with a one-timer off a Marchessault pass from the behind the net.

The Maple Leafs closed to with 4-3 on a pair of goals by Matthews over a 74-second span, the first on a wrist shot followed by rebound of a Morgan Rielly shot just 27 seconds into the third period.

"I got a little scared actually when they scored that third goal in the third period on that first shift," Gallant said. "Matthews and that line were unbelievable. They've got great puck possession and they make great plays."

But Marchessault made it 5-3 off a pass from Karlsson after an end-to-end rush by defenseman Shea Theodore, and Karlsson sealed it with an empty-netter at 18:24, outracing Rielly down the right side and then diving and flicking his stick at the puck in the right circle.

"I don't think I've ever skated so fast in my life," Karlsson said. "I really wanted it. I just threw myself and I whipped my stick at it. It was a great feeling to see it go in. It was pretty surreal to see all the hats falling down. You dream about that your whole life."

"It was great," Gallant said of Karlsson's hat trick. "He made an unbelievable effort to get that third goal. He dove and knocked the puck in, so it was a perfect ending."

NOTES: C William Karlsson now has nine first-period goals this season, which ties him with Washington's Alex Ovechkin for most in the NHL. ... Vegas returns to action on Tuesday with a home game against Nashville while Toronto opens a six-game homestand on Tuesday against Tampa Bay. ... D Connor Carrick, G Curtis McElhinney and C Nazem Kadri were scratched by the Maple Leafs while C Ryan Carpenter and D Brad Hunt were scratched by the Golden Knights.