The club didn't release terms, but a source told ESPN's Dan Graziano that the deal is for one year and $12 million guaranteed with $2 million in possible incentives.
The Rams, with a pressing need for an edge rusher, completed a trade for Fowler with the Jacksonville Jaguars ahead of the deadline last season in exchange for a third-round draft pick in 2019 and a fifth-round selection in 2020.
Fowler, 24, played in 11 games for the Rams after the trade, including three in the postseason, and made nine starts. In his six regular-season starts, Fowler finished with a pass deflection, fumble recovery, two sacks and five quarterback hits.
In Week 10 against the Seattle Seahawks, Fowler strip-sacked Russell Wilson and recovered the fumble midway through the fourth quarter. The Rams scored on the following play to secure a victory. In the NFC Championship Game, the 6-foot-3, 255-pound Fowler had a key pressure on Drew Brees that forced the veteran Saints quarterback to throw an errant pass that was intercepted in overtime.
The Jaguars selected Fowler from Florida with the third overall pick in the 2015 draft, but last May declined to pick up the fifth-year option on his rookie contract. Fowler did not play his rookie season because of a torn ACL. He had four sacks in 2016 and eight sacks in 2017. Fowler played in seven games with the Jaguars last season and collected two sacks before he was traded to the Rams.
He had a long list of off-the-field issues with the Jaguars but had no known such problems with the Rams. In 2016, Fowler was captured on video apparently refereeing a fight between his girlfriend and the mother of his child. Weeks later, he was arrested and charged with misdemeanor counts of assault against a police officer and resisting arrest without violence. The charges were later dropped.
Fowler also was involved in several fights during Jaguars practices and was suspended for one week during training camp. He also was suspended for the 2018 season opener after he pleaded no contest to charges of battery, criminal mischief and petit theft following an arrest in July 2017 in his hometown of St. Petersburg, Florida. Fowler also was issued more than 10 traffic citations over the span of two years.
ESPN's Lindsey Thiry contributed to this report.