Who won the first UFC women’s fight at UFC 157?

Ronda Rousey won the first UFC women’s fight at UFC 157.

UFC 157 took place on February 23, 2013, in Anaheim, California. Rousey defended the UFC Women’s Bantamweight Championship against Liz Carmouche in the first women’s bout in UFC history. Rousey won by armbar submission in the first round.

Carmouche briefly threatened Rousey with a rear-naked choke and a standing neck crank, creating one of the most dramatic opening rounds of the early women’s UFC era. Rousey then returned to her trademark grappling and finished the contest with an armbar.

This question concerns the first women’s fight in the UFC, not the first women’s championship fight in another organization. Rousey had already become the UFC’s inaugural women’s bantamweight champion at UFC 157, while Carmouche was the challenger.