Henry Cejudo became the first Olympic champion to win a UFC belt in the UFC history. Cejudo beat the defending champion, Demetrious Johnson in UFC 227 in Los Angeles.
Which UFC champions have been medal winners in the Olympics?
Looking at UFC after introduction of weight classes, here is the list of UFC champions I found to have also won an Olympics medal:
Ronda Rousey was a UFC Champion and has a bronze medal in judo.