The 27-year-old defenseman is in the final season of a six-year, $30 million contract ($5 million average annual value) he signed with Toronto on April 13, 2016 and could have become an unrestricted free agent after the season.
"I feel very good right now," Rielly said. "I felt good in training camp. I didn't want to be a distraction but I had a feeling it was going to get done at some point. But you just try not to think about it. The way it got handled from both sides was good."
Rielly has four assists in eight games this season. He is the longest-tenured player on the Maple Leafs and has been an alternate captain since 2016.
"Morgan is a steadying force and a great person who leads by example," Maple Leafs general manager Kyle Dubas said. "With the commitment when you're signing someone for eight years, you need to know the person you're signing. That makes you more comfortable where you know he's going to have a lot of pride in himself as he said to me last night in carrying his end of the deal and performing throughout those eight years. A lot of people you hear that from and you don't know, with Morgan you know.
"The work he puts in and his attention to continuing to improve and get better. His mobility is one area that leads me to believe the deal will age well with him. His evolution as he's maturing as a person, what he's been able to take on, we have a lot of faith in him performing well throughout the term."
The signing means the Maple Leafs now have their core of Rielly, defensemen Jake Muzzin and TJ Brodie, and forwards Auston Matthews, Mitchell Marner, John Tavares and William Nylander each signed through the 2023-24 season.
"I believe in the group we have here and for the team to offer me that notion of faith is pretty special too and I look forward to holding up my end of the bargain and accomplishing the ultimate goal," Rielly said.
Selected by Toronto with the No. 5 pick in the 2012 NHL Draft, Rielly has scored 309 points (59 goals, 250 assists) in 580 regular-season game and 19 points (four goals, 15 assists) in 32 Stanley Cup Playoff games.
He ranks seventh all-time among Maple Leafs defenseman in points, tied for 11th in goals, fifth in assists and seventh in power-play points (100). He's scored at least 27 points in each of his first eight NHL seasons.
Rielly finished fifth in voting for the Norris Trophy as the best defenseman in the NHL in 2018-19 when he scored a career-high 72 points (20 goals, 52 assists) in 82 games.
"It's a nice message from Morgan to the team that he believes in what we are doing here," Maple Leafs coach Sheldon Keefe said. "He has incredible integrity, he's a great teammate and leader and works incredibly hard. He puts the team ahead of himself and he's a very selfless player. The talents he has are a huge part of what he brings but there's all those other intangibles.
"There's a reason why the organization has gone through a number of changes over the years but he's the one guy who has lasted. That passion and commitment he has to the organization comes through in the way he conducts himself every day."
NHL.com staff writer Mike Zeisberger and independent correspondent Dave McCarthy contributed to this report
