The move will happen before the start of the new league year March 15, a source told ESPN.
Fournette told the Tampa Bay Times that he asked for his release and that's there "no bad blood" between him and the franchise.
Last offseason, the Bucs signed Fournette, the fourth overall draft pick in 2017, to a three-year deal worth $21 million and up to $24 million with incentives. But the Bucs enter the 2023 offseason a projected $55 million over the salary cap -- $35 million of it coming from retired quarterback Tom Brady.
Fournette told the Times that Brady's retirement was a factor in his decision.
"Winning is everything," Fournette told the newspaper. "That's all. And in my last three years here, that's all we've done. But since my guy [Brady] left, that's why I came, so my time here was up."
Fournette has $2 million in guaranteed money remaining on his contract.
"That's part of the business, part of it. You know, the business side of it is always ugly," coach Todd Bowles said of his team's cap situation. "Anytime you have a good team, you're gonna have some expensive players, and when it's time to pay the piper, you gotta start to make some cuts and make the smart decisions without undercutting your team. But at the same time, going forward and getting some young guys in here that can replace 'em and play."
The Buccaneers had the NFL's worst rushing attack in 2022, averaging 76.94 rushing yards per game, with Fournette rushing for 668 yards on 189 carries with three touchdowns while the interior offensive line was forced to contend with the losses of center Ryan Jensen to injury, right guard Alex Cappa to free agency and left guard Ali Marpet to retirement.
Fournette also had 523 receiving yards with three touchdown catches in 16 games last season. In three seasons with the Buccaneers, he had 3,057 total yards and 22 touchdowns.
Tampa Bay is having to make difficult choices, especially with just one quarterback now on the roster: Kyle Trask, who will get a shot to compete for the starting job.
"We have some tough decisions to make," general manager Jason Licht said Tuesday at the scouting combine, adding, "especially when you're talking about players that helped you win a Super Bowl."
The Buccaneers also saw promise in running back Rachaad White, who rushed for 481 yards in his rookie year, starting eight of 17 regular-season games.
"Rachaad is a good, young back that is just scratching the surface of what he can do," Licht said at the combine. "Ke'Shawn [Vaughn] -- I don't think he really has had a fair opportunity to show what he can do and what we know he can do from practice."
Licht, who did not confirm that Fournette will be released, said he believes the veteran running back "still has several years left in him as a three-down back."
Fournette, who earned the nickname "Playoff Lenny" and later "Lombardi Lenny," was set to earn $2 million had he been on the roster on the third day of the new league year. He would have carried an $8.47 million cap hit in 2023.
NFL Network was the first to report the move.