Mayweather?s social media post also included a video of him talking to Pacquiao, 39, at an event in Japan.
?I?m coming back in December,? Mayweather, 41, can be heard telling his entourage.
Mayweather didn?t mention where the rematch would take place.
In 2015, Mayweather and Pacquiao delivered a dud at the MGM Grand Garden Arena after a seven-year buildup.
Mayweather?s unanimous decision over Pacquiao was the most lucrative bout in boxing history.
In July, Pacquiao recorded a technical knockout against Lucas Matthysse to win a secondary WBA welterweight title.
For the second year in a row, Mayweather stole thunder from a Saul ?Canelo? Alvarez and Gennady Golovkin bout.
It?s probably no coincidence that Mayweather made this announcement on the day Alvarez and Golovkin meet for their rematch at T-Mobile Arena.
Last year, Mayweather defeated Conor McGregor a month before Alvarez and Golovkin fought to a split draw.
