It was last December that Peña defeated the legendary Amanda Nunes via choke in the second round at the UFC 269 event where Conor McGregor and Dustin Poirier were the main match.
The hard-hitting Nunes entered the match with twelve straight victories and the status of the top female MMA fighter of all time.
But that night, Julianna Peña took over the UFC bantamweight belt.
The night before Sunday they meet again at UFC 277 in Dallas, Texas.
- Amanda and I are the world's two best female fighters.
It's the two absolute best colliding.
All I can say is that I will meet her in the middle and not budge an inch.
I will do my very best and we will see who has the biggest ovaries, but I can bet that it is me, says Peña during a press conference.
Amanda Nunes - who before the loss went undefeated for six years - says she has been re-ignited by now being a contender again.
- I need something that pushes me a little extra and Juliana is the challenge I need.
For so many years I have been looking for this challenge and now I am finally in the position where I feel threatened.
That's when I shine the most, says the Brazilian.
Peña has an 11-4 fight record while Nunes has won 21 of his 26 pro fights.