Terms of the contract weren't officially announced, but Tannehill received a deal worth $118 million over four years with $91 million in guarantees, a source told ESPN's Jeff Darlington.
Under his reported deal, Tannehill would rank seventh among all quarterbacks in terms of average annual salary ($29.5 million), according to Spotrac.
By re-signing Tannehill, Tennessee is now free to use its lone franchise/transition tag on star running back Derrick Henry.
The deal came shortly after it reported that Tennessee wasn't interested in pursuing Tom Brady and was instead focusing on re-signing the 2019 Comeback Player of the Year. The Titans were initially believed to be among the favorites to sign the longtime New England Patriots quarterback this offseason.
Tannehill revitalized his career in 2019 after taking over for Marcus Mariota and starting 10 games. Despite originally being signed as a backup, Tannehill produced the best regular season of his career and led the Titans to their first AFC Championship Game since 2003.
The 30-year-old topped the NFL in passer rating and yards per attempt while throwing for 22 touchdowns and just six interceptions.