The deal will pay Gallagher $5.5M in 2015-16, $4.5M in 2016-17, $2.75M in 2017-18, $3M in 2018-19, $4M in 2019-20 and $2.75M in 2020-21.
"It's never about the money. The most important thing for me was getting the six years," said Gallagher. "When that was proposed, I was just excited to have the opportunity to continue to build on what we have. We have a great group of guys, guys who want to come to the rink and improve every day."
Gallagher has five goals and seven assists in 24 games with Montreal this season. In 149 regular-season games with the Canadiens, the 22-year-old has recorded 81 points (39 goals, 42 assists).
"He doesn't take a shift off, he never has," said Canadiens general manager Marc Bergevin. "The effort is always there, and his character is off the charts. He's always in the paint, he works hard, he gets loose pucks, and he's not afraid of anything. He competes night in and night out.
"The way Brendan performs on the ice, he's always around the net. Whether you're six-foot-eight, or six-foot-one, he plays the same way. His foot is always on the accelerator."
The Edmonton native was selected by Montreal in the fifth round of the 2010 NHL draft — 147th overall. He was named to the NHL all-rookie team in 2012-13.
"Brendan has shown from Day 1 that he loves Montreal, and he wants to be a Montreal Canadien," said Bergevin, who added the deal was roughly one month in the making. "He's proud, and he loves the city and its fans. That made it even easier."
The deal means Gallagher will don a Canadiens sweater until the end of the 2020-21 season. Bergevin, historically reticent to follow an entry-level deal with a long-term extension, said Gallagher's contract made a lot of sense for the organization.
"At the end of the day, we feel comfortable," said Bergevin. "It's always a risk going long-term with any player. We felt this time that the risk was worth it."
"To have that kind of trust and commitment coming off an entry-level deal is definitely pretty cool," said Gallagher. "It's something I'm very appreciative of. Now I have to show them that they made the right decision putting their trust in me."