Boxing legend Leon Spinks -- who famously beat Muhammad Ali in 1978 -- is fighting for his life in a Vegas hospital, TMZ Sports has learned ... and his wife is asking for prayers.
Details surrounding the 66-year-old's condition are unclear -- but we know his family and friends are very concerned.
In fact, Leon's wife, Brenda, went to social media saying, "Reaching out to ask you to kindly send some prayers out for my Beautiful Husband Leon so that he may overcome the obstacles that have crossed his path.