As part of the deal he signed to play with the LA Galaxy in 2007, Beckham had the option to start a new team for a heavily discounted expansion fee of around $25 million.
A statement released on the MLS website revealed that the team will play in a privately developed 25,000-seat stadium within the city.
The launch follows four years of disputes over the site for a stadium in southern Florida, with residents having opposed multiple locations. "It's a sport that I've loved for many, many years", he said. But that was abandoned in late 2015 over what the partnership said was overpriced real estate, and the Beckham group declared Overtown the future home of MLS in Miami.
The press conference took place at Miami's Adrienne Arsht Center and members of Beckham's ownership group were also be present.
Beckham has spent the last four years trying to bring MLS back to South Florida.
Futbol Miami's debut season in MLS is yet to be finalised but Beckham is targeting the 2020 campaign and hopes to bring in major names from European football, while cultivating youth talent.
"There have been many (hurdles)", Beckham said.
Beckham and his partners weren't the only ones to welcome a team to Miami: the crew enlisted some starpower with a welcome video featuring Serena Williams, Will Smith, Neymar, Jay-Z, Alex Morgan, and more (turns out we have J.Lo to thank for all this).
"Being a native, I'm a Miami guy 1,000 percent, and I want to make this a really special team with a really special fan experience".
Beckham previously had endured years of frustration over the Miami MLS project, as he sought investors and a suitable stadium site.
MLS Commissioner Don Garber is among those expected to attend, along with several Miami-Dade County political officials.
"It was hard at times", he said. "There are other venues in this town that would be pretty good temporary sites".
The owners of Los Angeles FC, which joins the league in March, are reported to have paid over $100 million for their franchise rights.
Beckham, 42, retired in 2013 after a 20-year career that saw him win league crowns with Manchester United in England, Real Madrid in Spain, the Galaxy in North America and Paris Saint-Germain in his farewell matches.