LAS VEGAS -- Floyd Mayweather Jr. will return to the ring for the first time since boxing's richest fight ever, facing Andre Berto on Sept. 12 in Las Vegas.

Mayweather posted an announcement of the fight Tuesday on several social media outlets. The bout will be televised on pay-per-view by the Showtime network.

Mayweather, who made more than $200 million for his fight May 2 against Manny Pacquiao, doesn't figure to make nearly as much against Berto. It will be the last in a six-fight deal Mayweather has with Showtime, after which he has said he will retire.

Mayweather has won all 48 of his fights and will be a lopsided favourite against Berto (30-3), who was once touted as a rising star in boxing but has lost three of his last six bouts.