The 27-year-old could have become an unrestricted free agent July 1. The contract has an average annual value of $5 million.

"Really happy, more happy to be here with my teammates," he said. "And the organization has done amazing things for us. Just everything since we all came here we just feel a part of a big family, and we love this city, and everybody wants to stay here, I'm pretty sure."

Chosen from the Florida Panthers in the 2017 NHL Expansion Draft on June 21, Marchessault leads Vegas with 37 points (15 goals, 22 assists) in 35 games playing on a line with William Karlsson and Reilly Smith.

"He fits our identity of a guy who competes on both ends of the rink, and he's generating offense," general manager George McPhee said. "We like how the line he's on is performing and wanted to keep it together."

Marchessault had NHL career highs of 30 goals and 51 points for the Panthers last season.

"We were hoping he wouldbe this kind of player," McPhee said. "It's not easy scoring 30 goals in this league, and he's playing at a level where he can do it again this season."

An undrafted free agent, Marchessault has 107 points (53 goals, 54 assists) in 159 NHL games with the Columbus Blue Jackets, Tampa Bay Lightning, Panthers and Golden Knights.

"It was never easy," Marchessault said. "Everything was always hard for me, and [to] play four years in the [American Hockey League], this is hard for your mental [game]. And I think I'm happy with the path that I took, and I'm just happy to be here, and I think it's going to be a great experience for our whole team, and we've started something great and we want to keep going, for sure."

Vegas (27-9-2) has won eight straight games, an NHL record for a team in its inaugural season, and is in first place in the Western Conference with 56 points, three ahead of the Los Angeles Kings and Winnipeg Jets.

Forwards James Neal and David Perron, and defenseman Deryk Engelland are other Golden Knights who can become unrestricted free agents July 1.

"We were focused on this deal at this time," McPhee said. "It felt like the right thing to do."

The Golden Knights play the St. Louis Blues at Scottrade Center on Thursday (8 p.m. ET; FS-MW, ATTSN-RM, NHL.TV).

"I'm never, never, never satisfied with what I've done in the past," Marchessault said. "I always want to beat what I did before, and every night I have one goal, is to help my teammates to win a hockey game. And I think we've been doing a good job, but there's a lot of hockey left so we can accomplish what we want."

NHL.com correspondent Danny Webster contributed to this report.