The deal contains more than $17 million in guarantees, according to sources.
The Bears had placed their franchise tag on Forte in March and the sides had until 4 p.m. ET on Monday to reach an agreement. Without a long-term deal, the Pro Bowl running back would have had to play the 2012 season under the $7.749 million tender or sit out the season.
The signing ends nearly a year of what one source characterized as sometimes-contentious negotiations. It also ensures Forte will be in the fold when the club begins training camp July 26 at Olivet Nazarene University.
"I'm proud to be a Chicago Bear and excited to be here for another four years," Forte said in a statement released by the team. "I've been working hard this offseason and am looking forward to joining my teammates at training camp next week."
Of the 21 players around the NFL given the franchise designation by their respective teams this year, 12 reached long-term contracts, six signed their one-year franchise tender offers, and three more remained unsigned.
Forte hinted in recent weeks there was a possibility he would hold out if he couldn't secure a new deal by Monday's deadline.
Forte's agent, Adisa Bakari, didn't respond to a message seeking comment.
"We're very pleased we were able to come to terms on a four-year extension with Matt," Bears general manager Phil Emery said. "We're excited to get him on the field and continue working towards our goal of winning a championship."
Because he wasn't under contract and hadn't signed the franchise tender, Forte missed the club's offseason conditioning program, organized team activities and mandatory minicamps. The Bears are installing a new scheme under offensive coordinator Mike Tice.
Quarterback Jay Cutler said last week that although Forte could expect subtle changes to the new scheme, he expected the running back to pick up the offense quickly.
"If and when we get Matt back, we're happy to have him," Cutler said. "I think physically, he can do it, no question about it.
The guy is an absolute gym rat. Running game wise, we have a lot of rollover (from last season). There's gonna be a little bit of change.
There's gonna be some verbiage that Matt's gonna have to learn. But Matt's one of those very, very smart, intellectual players. He picks things up the first time he does it. I'm not worried about Matt. If we have a short amount of time with Matt, he's gonna be fine."
A five-year veteran, Forte averaged a career-best 4.9 yards per carry in 2011 en route to earning Pro Bowl recognition for the first time after producing 1,487 yards from scrimmage, including 997 yards rushing. Forte missed four games with a sprained right medial collateral ligament after a hit from Kansas City linebacker Derrick Johnson in a Dec. 4 loss at Soldier Field.
At the time of the injury, Forte was leading the league in yards from scrimmage.
Since entering the league in 2008, Forte ranks sixth in the league with 6,218 yards from scrimmage and is the only player in NFL history to gain 900 yards rushing and 400 receiving in each of his first four seasons. Forte is also one of four Bears to gain at least 4,000 rushing yards (4,233) and 1,500 receiving yards (1,985) in his career.
Despite missing four games, Forte finished last season ranked third in the NFL in scrimmage yards per game (123.9).
But even with Forte's productivity, the Bears were hesitant to extend the rich payday the running back thought he deserved. Before the start of the 2011 season, the Bears offered Forte a five-year contract worth a little more than $15 million guaranteed.
Earlier this offseason the club signed former Oakland Raider Michael Bush in free agency as a backup to Forte; a move widely viewed as somewhat of a contingency plan for a potential Forte holdout.
A little more than a month ago, the club had increased the offer to more than $16 million, according to a source.
Although it appeared the sides were far apart at the time, Forte continued to express optimism that a deal could be struck before the deadline.
"I'm glad the business part is done," he said Monday. "We can all turn our attention to football and our goal of winning a championship."