Nelson Thomas -- a star on MTV's "The Challenge" -- just revealed he is the man NFL player K.J. Osborn and three others helped pull from a fiery car crash earlier this month ... thanking the group for saving his life.
As we previously reported, the Minnesota Vikings receiver said he was in an Uber heading home after a workout in Austin, Texas on March 5 ... when he saw a car that had crashed and caught fire.
Osborn, his driver and two others rushed to assist .