The unbeaten 38-year-old, who is now 48-0-0-KO26 and holds the WBC, and WBA (super) world welterweight titles, outpointed Pacquiao in Las Vegas in a bout that smashed pay-per-view records.
Mayweather, who was stripped of the WBO version of the belt earlier this week, posted on social media: “To My fans, your loyalty and support has given me the best 20 years I could ask for and while at the top, I plan to go out on top???.see you back in the ring September 12th!”
The news will crank up speculation over the identity of his next opponent.
Mayweather has previously earmarked Andre Berto (30-3-0-KO23) and Karim Mayfield (19-2-1-KO11) as those leading the race to face him next – but those prospective bouts have been slammed by other suitors.
Former world champion Amir Khan has long been pursuing a clash with the American and has claimed on several occasions that an announcement was close to being made.
Kell Brook and Keith Thurman – the IBF and WBA welterweight champions respectively – have joined the hunt for the lucrative showdown, while middleweight king Gennady Golovkin has also thrown his hat in to the ring.