Ramsey becomes the first defensive back in NFL history to sign a deal worth over $100 million, and his $71.2 million at signing is the largest guarantee to a defensive back.
The Rams announced the five-year agreement Wednesday without providing the value.
"I'm happy for Jalen and I'm happy for our football team," coach Sean McVay said Wednesday. "I think for him to be able to get that taken care of, you don't have any sort of distractions in the background, so that's definitely a positive for us."
The previous largest contract for a cornerback in terms of average annual value was Darrelle Revis' $18.2 million per year, when he signed a six-year contract in 2013 after being traded from the New York Jets to the Tampa Bay Buccaneers. Revis was released the following offseason.
An All-Pro and a three-time Pro Bowl selection, Ramsey becomes a long-term fixture on a defense that includes two-time NFL Defensive Player of the Year Aaron Donald, who signed a six-year, $135 million extension before the 2018 season.
At the beginning of training camp, Ramsey, 25, said he was not worried about an extension as he prepared to enter the final season of his rookie deal, valued at $13.7 million.
"I'm trying to do my job as a football player. I'm trying to be a leader on the team," Ramsey said. "If it comes, it comes. It's going to be a surprise to me, like it's going to be a surprise to you all."
McVay has said Ramsey dominated training camp, his first with the team.
"I thought I had an appreciation for the way that he played and just watching him from afar," McVay said. "But now, really getting a glimpse and with the amount of competitive work we're getting in these training camp settings, he's even better than I thought."
First-year defensive coordinator Brandon Staley is expected to use the lockdown cornerback in a variety of ways this season. Ramsey said before training camp that he would like to be considered a defensive back in 2020 rather than a cornerback.
"I think we fit really well together and that we've gotten to learn a lot more about each other over the last six months and certainly the last month and change since we've been in person," Staley said about his rapport with Ramsey. "We're hoping the best is to come."
The Rams acquired Ramsey last October, sending their 2020 and 2021 first-round picks and a 2021 fourth-round pick to the Jacksonville Jaguars, who selected Ramsey with the fifth pick in the 2016 draft, the year the Rams selected Goff No. 1 overall.
In nine games with the Rams last season, Ramsey intercepted a pass and had four pass deflections and a forced fumble.
His arrival in Los Angeles marked a fresh start after a bumpy tenure in Jacksonville, which came to a head in the first half of the 2019 season.
After a Week 2 loss at Houston, then-Jaguars executive vice president of football operations Tom Coughlin admonished Ramsey for his actions during the game, which included a sideline shouting match with coach Doug Marrone.
Ramsey played the following Thursday against the Tennessee Titans but did not practice the following Monday because of an illness. He then missed Wednesday's practice because of a back injury, and on the same day, it was announced that Ramsey would return to his hometown of Nashville, Tennessee, for the birth of his second daughter. Ramsey spent the next three games inactive because of the back issue, then was traded to the Rams, where he was immediately cleared to play.
On an episode of "Hard Knocks: Los Angeles," Ramsey said that Oct. 15, the day he was traded, was "probably one of the best days of my life."
In 60 career games, Ramsey has intercepted 10 passes, returning one for a touchdown, and has 49 pass deflections and three forced fumbles.