Miesha Tate: I Won My First Fight ... IN 3RD GRADE!!!

Miesha Tate won her first fight at 8 YEARS OLD ... beating up a boy in a violent turf war ... and it changed her life forever!!

The UFC superstar sat down with TMZ's Charlie Cotton to promote UFC 200 on July 9th -- when she regaled us about the first time she opened up a can of whoopass.

"The boy was a year older than me," Miesha said.