Brian Viloria stopped Hernan Marquez in the 10th round to add the WBA world flyweight title to his own WBO belt in Los Angeles on Saturday evening.
Viloria knocked Marquez down with a right late in round one and continued to dominate the early rounds, before a flurry from the Mexican in the fifth forced him onto the defensive.
When Viloria put Marquez on the floor for a third time with a left to the head in the 10th, Marquez's corner threw in the towel.
On the undercard, Nicaragua's Roman Gonzalez defended his WBA world light-flyweight title against Mexican Juan Francisco Estrada.
Gonzalez claimed a unanimous decision with the judges scoring it in his favour by margins of 116-112 twice and 118-110.
The 25-year-old is now 34-0 (28KO) as a professional.