Floyd Mayweather Jr. gave himself a 37th birthday present on Monday: an opponent. The pound-for-pound king announced on Twitter that he will next fight fellow welterweight titleholder Marcos Maidana on May 3.

The 147-pound unification fight will be carried by Showtime PPV and take place at a venue to be determined — either in Las Vegas at the MGM Grand, the front-runner, where Mayweather has had his last eight fights, or the Barclays Center in Brooklyn, N.Y., which came into the picture in recent weeks and is making a strong push for the fight.

Golden Boy Promotions chief executive Richard Schaefer, who has worked with Mayweather since 2007 and also promotes Maidana, told ESPN.com that he hopes to have the venue locked in “in the next couple of days along with the ticket information.”

The fight will be the third of a 30-month, six-fight deal worth $200 million-plus that Mayweather signed with Showtime and parent network CBS last February. Mayweather has said he plans to retire at the conclusion of the contract.

Mayweather (45-0, 26 KOs) holds world titles at junior middleweight and welterweight but will return to welterweight to make his second defense when he faces Maidana (35-3, 31 KOs), a 30-year-old crowd-pleasing slugger from Argentina who will be making the first defense of his belt. Maidana, who landed the fight over fellow former junior welterweight titlist Amir Khan, won his world title in dramatic upset fashion by scoring two knockdowns in a unanimous decision against Adrien Broner in their Dec. 14 brawl at the Alamodome in San Antonio.