Brandon Moreno is the 1st Mexico-born UFC champ … and the newly crowned flyweight king just received a heartfelt message from Mexico’s arguably greatest athlete ever — and it’s impossible for this to not make you feel good.

TMZ Sports recently talked to 58-year-old Julio Cesar Chavez Sr. (he’s fighting this weekend) … and we asked the former boxing superstar if he had a message for Moreno following his historic victory.

We played the message for the 27-year-old, Assassin Baby … and it was awesome.

Chavez’s message … “A lot of blessings, and remember that the difficult part is not to get where he is at, but to endure. That’s the tough part. Blessings and God bless.”

Moreno’s reaction … “Man, that is crazy. That definitely crazy, you know? He’s an example for me. Actually, it’s not just for me, I think for every single Mexican, for the fans of boxing, for the fans of combat sports around the world.”

Brandon continued … “Julio Cesar Chavez is a legend. A living legend in Mexico and that makes the message for me so special, and I’m very grateful to hear that.”

We also talked to Brandon about who he wants next … and whether a trilogy fight with Deiveson Figueiredo — who BM submitted in the 3rd round at UFC 263 — could be in the works.

“[Deiveson’s] always a possibility, you know? He’s the former champ, he looks impressive in his last performance, but I don’t know, man,” Moreno says.

“I don’t know what to think, but to be honest I think the fight was very dominant by myself.”

Since he clearly isn’t feeling a rematch — at least not right now — Moreno did throw out a few possible opponents that he’d like to fight later this year.