John Cena busted out a ring IN THE RING ... popping the question to a fellow WWE superstar Nikki Bella -- and like her brother-in-law Daniel Bryan she said, 'YES! YES! YES!'
Cena whipped out the massive Tiffany diamond after he and Nikki beat up The Miz and Maryse in a co-ed tag team match at Wrestlemania 33.
Here's the thing ... Cena didn't use her "ring name" -- he proposed with her real name, "Stephanie Nicole Garcia-Colace" -- leading most people to think the proposal was real and not a scripted bit.
John and Nikki have been dating in real life since 2012.