The 36-year-old striker has reportedly been offered €400m (£344m) a year to join Saudi club Al Hilal and has also been linked with a move back to his former club Barcelona.
Lionel Messi has signed with Inter Miami, the club announced.
The Argentine superstar joined David Beckhamclub, and his contract will be until 2025.
The World Cup winner said in a statement from the club: “I am very excited to begin this next step in my career with Inter Miami and in the United States.
“This is a fantastic opportunity and together we will continue to build this beautiful project. The idea is to work together to achieve the goals we have set for ourselves and I am very eager to start helping out here in my new home.”
Beckham said he was very happy about Messi’s arrival and described him as “a good friend (and) an amazing person”.
He said: “Ten years ago, when I started my journey to build a new team in Miami, I said my dream was to bring the greatest players in the world to this incredible city.
“Players who shared the ambition I had when I joined the LA Galaxy to help grow soccer in the US and build a legacy for the next generation in the sport we love so much.”
“Today that dream came true.”
The England and Manchester United legend added: “I couldn’t be more proud that a player of Leo’s caliber is joining our club.”
The 36-year-old striker’s contract with Paris Saint-Germain expired at the end of June.
Inter Miami CF managing owner Jorge Mas said: “It is an honor to welcome Leo Messi and his family in their new home.”
Earlier in the year Phil Neville has been sacked as manager of Inter Miamiwhich are co-owned by his former Manchester United team-mate and England Beckham.
Florida is currently at the bottom of the 15-team Eastern Conference with just five wins in 16 games.
Messi will first be available for selection for Inter Miami on July 21 when they face Mexico’s Cruz Azul in the first leg of the League Cup.
The League Cup is a new tournament in which MLS and LIGA MX, Mexico’s top division, will interrupt their respective league seasons from July 21 to August 19 to determine the three clubs that will qualify for the 2024 CONCAF Champions Cup.