1. Joanna Jedrzejczyk
Before owning the UFC Strawweight division, Joanna Jedrzejczyk was a 5x IFMA World Muay Thai champion. Her pro kickboxing record is listed as 27-2, but she competed in many more amateur bouts.
Joanna transitioned from kickboxing to MMA in 2012, and has been dominant ever since. She won her first 6 fights before being signed by the UFC. After winning her first two fights, Joanna knocked out Carla Esparza to win the UFC Strawweight Championship.
Next up for Joanna will be Karolina Kowalkiewicz at UFC 205.
