Terms were not disclosed but it's a three-year deal worth up to $39 million, a source told ESPN's Adam Schefter. The contract includes $18 million guaranteed, a source told ESPN's Dan Graziano.
It marks a homecoming for Williams, who was born in Jacksonville. He is the second cornerback in two years to sign a multiyear contract in free agency with the Jaguars, as Shaquill Griffin joined the franchise last year on a three-year contract.
Williams will join a loaded free-agent group for the Jaguars that includes wide receivers Christian Kirk and Zay Jones, tight end Evan Engram, guard Brandon Scherff, linebacker Foyesade Oluokun and defensive tackle Folorunso Fatukasi.
Williams, 29, played 14 games with 13 starts during the 2021 regular season and started all four playoff games for the Super Bowl-champion Rams.
He missed three games last season while on injured reserve with an ankle injury.
The Rams claimed Williams off waivers from the Baltimore Ravens in 2018. He has played 42 games total for Los Angeles, becoming a full-time starter for the Rams last season. He had a career-high four interceptions in 2020 and has six in his four NFL seasons.
He went undrafted out of UAB in 2018 and signed with the Ravens, playing three games for Baltimore that season before being waived.