Wagner agreed to terms on a five-year contract with the Super Bowl champion Los Angeles Rams, the team announced Thursday.
Financial terms were not disclosed, but sources told ESPN's Adam Schefter the deal is for $50 million and can be worth up to $65 million if Wagner reaches incentives.
It will mark a homecoming for Wagner, who was born in Los Angeles and attended high school in Ontario, California, about 35 miles east of the city. Wagner becomes the latest big-name player to join a star-studded Rams defense that already includes defensive tackle Aaron Donald and cornerback Jalen Ramsey.
Donald (five), Wagner (four) and Ramsey (three) have all earned at least three first-team All-Pro selections over the past five seasons. Only six defensive players in the NFL have achieved that feat over that time period, according to ESPN Stats & Information research.
The Rams had a need at one of their inside linebacker spots after they declined to tender Troy Reeder as a restricted free agent.
Wagner publicly and privately voiced his unhappiness over how the Seahawks handled his release earlier this month. Seahawks general manager John Schneider and coach Pete Carroll expressed their regret over how they communicated those plans to Wagner.
Wagner, 31, was the last remaining member of the star-studded defenses that led Seattle to its lone world championship and a return trip to Super Bowl XLIX after the 2014 season.
Wagner, the Seahawks' all-time tackles leader with 1,383, is coming off a 170-tackle season that earned him his eighth Pro Bowl nod in 10 seasons. He posted that personal best despite missing all but one snap of the final two games with a knee sprain.
While Wagner didn't make as many impact plays as in some of his best seasons, he recorded an interception, a sack, a forced fumble and five passes defended in 2021 en route to a second-team All-Pro selection.
In 2020, Wagner was one of 22 defenders named by the Pro Football Hall of Fame to the All-Decade Team for the 2010s. His Hall of Fame-worthy résumé also includes six first-team All-Pro selections, two second-team All-Pro selections and eight Pro Bowls nods, tied for second most in franchise history.
ESPN's Brady Henderson contributed to this report.