Los Angeles originally acquired Peters from the Kansas City Chiefs before the beginning of last season. In 22 regular-season contests with the Rams, he recorded five interceptions, returning two for touchdowns.
The Chiefs selected Peters in the first round (No. 18 overall) of the 2015 NFL Draft out of Washington. He made the Pro Bowl in the 2015 and 2016 seasons with the franchise.
Peters, who is in the final season of his rookie contract, will get a chance to play against the Rams in Week 12, when Los Angeles will host the Ravens on Monday Night Football.
The trade comes one day after the Rams placed fellow starting cornerback Aqib Talib on injured reserve with a rib injury. He will be sidelined for at least eight weeks before he is eligible to return from IR.
The Ravens, who have been hit by multiple injuries in their secondary, needed help in the defensive backfield. Cornerback Jimmy Smith has missed the last five games because of a knee injury, and nickel corner Tavon Young is out for the season with a neck injury.
Kenny Young started the season as the Ravens' weakside linebacker but fell out of the rotation after multiple mistakes. He was a healthy scratch in Week 5.