Josef Martinez has left Atlanta United for Inter Miami, replacing the retired Gonzalo Higuain.
Miami announced the deal on Wednesday after Atlanta confirmed they had agreed a contract buyout with the player.
Martinez had been with Atlanta since their debut MLS season in 2018 and is the club's record scorer with 111 goals.
In the 2018 season, he teamed up with Miguel Almiron to lead the Five Stripes to MLS Cup glory.
Martinez was the MLS MVP, MLS All-Star MVP and MLS Cup MVP in that campaign, as well as winning the Golden Boot and scoring the opening goal in the title match.
Atlanta went on to win the U.S. Open Cup and Campeones Cup the following year but have increasingly struggled since Almiron's record-breaking move to Newcastle United in the Premier League.
They missed out on the playoffs in two of the past three years, and Martinez has now moved on to join Eastern Conference rivals Miami.
Under Phil Neville, Miami enjoyed their best season in 2022, finishing sixth in the East, but Higuain's retirement had left a gaping hole in their attack.
"Josef is a champion and adding him to our group is exciting for us as we head into the 2023 season," said sporting director Chris Henderson.
"He's been one of the best players in the league since he first arrived and we believe he'll make a difference here at Inter Miami.
"We're adding a proven goalscorer with a track record of success in MLS. We're thrilled to have a player like Josef in our attack."
Martinez added: "I'm excited for the opportunity to represent Inter Miami and give the best of myself.
"This is a club with high aspirations and that aims to be amongst the best in the league. I hope to help the team achieve its objectives and leave my mark at the club."
Atlanta technical director Carlos Bocanegra said: "Josef has played a pivotal role in Atlanta United's history, scoring memorable goals and hoisting multiple trophies for moments that will forever live with our supporters.
"He was a foundational piece who was responsible for helping build our brand into what it is today.
"We cannot thank him enough for his contributions to the club and the community over the last six years. He will always be part of Atlanta United and we wish him the best of luck in his future endeavours."