Julien BriseBois, who had been Yzerman's assistant, takes over as GM. Yzerman is in the final year of his contract.
"To do the job the way it needs to be done and to be with my family as well, it's becoming difficult to do," Yzerman, 53, said. "Hence the decision. I will be wherever I'm needed to be for Julien moving forward.
"This new position will allow me to spend more time with my wife and three daughters who live and attend college in cities in the northern United States. At the direction of (owner) Jeff Vinik, this organization has been committed to excellence and it will remain so under Julien's guidance."
[RELATED: Yzerman timeline with Lightning | New GM BriseBois expects 'business as usual']
Since Yzerman was hired May 25, 2010, the Lightning have made the Eastern Conference Final four times, including three of the past four seasons, and reached the Stanley Cup Final in 2015, when they lost to the Chicago Blackhawks in six games.
"The name of the game is winning. You have to win," BriseBois said. "If anything, at least we're built to win right now. The reality is there's probably never been more teams that can legitimate aspire to the Cup as there are right now. ... Two years ago we didn't make the playoffs. So we need to have a really good camp, we need to have a really good start and start putting points in the bank right now because that kind of dictates a lot of the decisions that will get made over the course of the season as well. There are several teams that can aspire to the Cup, and I like the fact we're one of them. That makes this job more appealing. It's not more pressure, it's more appealing."
Among the moves made by Tampa Bay since hiring Yzerman was the signing of center Steven Stamkos to an eight-year contract on June 29, 2016, two days before he would have become an unrestricted free agent. They traded for defenseman Ryan McDonagh and forward J.T. Miller on Feb. 26.
"I met with Steve this morning, and I was shocked to say the least," Stamkos, the Lightning captain, told The Athletic. "But I respect his decision. I have had such a great relationship with Steve and it's tough to see him step down, but saying that, Julien has been there every step of the way and we have all the confidence in him going forward. Management and ownership have always been on the same page, with the same goal. And that is to win a Stanley Cup. And nothing is going to change that goal moving forward."
The Lightning hired Jon Cooper as coach March 25, 2013.
"I can't say enough about how much Steve Yzerman meant to me both in my professional career and in my personal life," Cooper said. "He's a mentor. He taught me things about the game, not only on the ice but how to deal with the players ... he's been in all those situations. He gave me my first crack at the NHL and I will forever be grateful to him for that. ... I know this isn't the end for us, but it's a tough day just because of how much he's meant to me."
Video: Yzerman steps down, Lightning name BriseBois new GM
Last season, the Lightning set their records for wins (54) and points (113) before a seven-game loss to the Washington Capitals in the Eastern Conference Final.
"In the role I am in, I am 100 percent committed this year, and we are going to do everything we can to win and have as successful a season as possible," he said. "Beyond this year, I don't have an answer."
BriseBois, 41, becomes the third-youngest general manager in the NHL behind John Chayka (Arizona Coyotes, 29) and Kyle Dubas (Toronto Maple Leafs, 32). BriseBois was named Lightning assistant GM and GM of their American Hockey League affiliate in Norfolk on July 16, 2010. Norfolk won the Calder Cup in 2012, and Syracuse, the Lightning's current AHL affiliate, made the Calder Cup Finals in 2013 and 2017. BriseBois said he will remain Crunch GM, at least to start the season.
"The reality is, in terms of being the guy and the decision-maker, I've been doing that for 12 years at the minor league level," BriseBois said. "The amount of autonomy I had in overseeing our player development both in Montreal for four years and my eight years here with Steve, I pretty much had carte blanche to run the program. So with regards to being the guy that has to make the decision, I'm comfortable with that, I'm used to that.
"I'm well surrounded by the people that we have in our organization and I'm excited about that, the fact that I'll be able to count on really good people that are good at what they do. I think the biggest difference is there's a lot more scrutiny at the NHL level than there is at the AHL level. That really is the most important difference, and time will tell how I handle that."
Yzerman is a member of the Hockey Hall of Fame and was named one of the 100 Greatest NHL Players presented by Molson Canadian. He had 1,755 points (692 goals, 1,063 assists) in 1,514 games over 22 NHL seasons, all with the Detroit Red Wings. The 10-time NHL all-star won the Stanley Cup three times (1997, 1998, 2002) and the Conn Smythe Trophy as MVP of the Stanley Cup Playoffs in 1998. He was executive director for Canada when it won the gold medal at the 2014 Sochi Olympics,
"He's even a better leader and general manager than people give him credit for," BriseBois said. "That's why it's really important to me that he stay on board and kind of be my sounding board going forward or for at least this year. And we'll revisit that at the end of the season. Hopefully he'll stay for more than one year."
NHL.com correspondent Corey Long contributed to this report.