"Win, Lose or Draw ... Deontay is our brother that has accomplished many triumphs and as a community we should all uplift and support him throughout it all," Mayweather posted on social media.
"No matter what, you're still a winner in my eyes, King!"
Wilder has exercised his rematch clause with Fury and is expected to get back in the ring for a 3rd fight with the Gypsy King on July 18 in Las Vegas.
Wilder has been catching flack for suggesting his 45-pound ring entrance costume had a lot to do with his poor performance against Fury ... after he claimed the weight of the outfit burned out his legs.
Over the weekend, Wilder posted a new video assuring his fans he's doing okay now -- and he's laser-focused on defeating Fury.
Will he strike a deal to train with Floyd? They do have a connection ... Wilder is managed by Al Haymon, Floyd's business partner.