As we previously reported ... 66-year-old Spinks -- who famously beat Muhammad Ali in '78 -- was fighting for his life after being diagnosed with prostate cancer, which spread to his bladder.

TMZ Sports has learned ... Spinks has made tremendous improvement and doctors recently cleared him to leave the hospital, which is a big deal considering how serious the situation was.

“Leon is home from the hospital and is slowly relearning his daily routine and getting physical therapy a few times a week," Spinks' rep tells us.

"He is in great spirits and has received an outpouring of love these past few months."

Matter of fact, Spinks tuned in to the Deontay Wilder vs. Tyson Fury fight alongside family and friends at his home last weekend ... and loved what he saw!!

"Leon thinks the heavyweight division of boxing is in great hands in the future with these two stars as well as guys like Anthony Joshua and Andy Ruiz who continue to put on great performances.”

Spinks is even getting back to work by doing a private autograph session with Inscriptagraphs in April ... where fans can get him to sign a bunch of awesome memorabilia.