Floyd Mayweather's stuffing his schedule with fights in 2026 -- not only is he slated to go up against Manny Pacquiao and Mike Tyson ... he's now booked an exhibition with another world champion in Greece.

TBE announced the bout against Mike Zambidis -- called the "Battle of the Legends" -- will go down at the Telekom Center in Athens this June ... three months before his pro rematch with Pac-Man and two months after his dance with Iron Mike.

Zambidis is a multiple-time title holder ... and has 157 wins on his kickboxing record. Floyd, of course, is 50-0 in the ring ... but since it's an exhibition, his 0 isn't going anywhere.

"2026 is already shaping up to be an exciting year for me...," the 49-year-old said on Monday. "(((Europe)))... I’m on the way to entertain!!"

"This summer will be a legendary battle 🔥🔥🔥June is the month where history will be made at the Telekom Center. Different energy. Different level."

Two Mikes and a Manny -- Floyd's looking to make easy work of these Ms and make some Ms in the process!!