Claressa Shields became the first undisputed champion of two weight divisions after sealing a shutout points victory over Marie-Eve Dicaire.
America's three-weight world champion is the only fighter, male or female, to hold every world title in two weight divisions in the four-belt era after her unanimous decision win over Dicaire, with three perfect scores of 100-90 in Flint, Michigan.
Canada's Dicaire had brought the IBF belt and an unbeaten 17-fight record into the bout, but she was outclassed by Shields, who had previously become undisputed champion at middleweight.
Shields made a typically aggressive start in the opening round, forcing Dicaire to seek refuge on the ropes after landing an early left hook.
The superior power of Shields continued to trouble Dicaire, who was knocked off balance by a hurtful left hand in the fourth round, while she was staggered by a crisp combination in the sixth.
Shields was eager to deliver a stoppage and another flurry of punches left Dicaire on shaky legs in the eighth round.
Dicaire did force Shields onto the back foot with a 10th round assault, although the two-time Olympic gold medallist easily picked her off with classy counter punches.
Promoter Dmitriy Salita had suggested earlier in the week that Shields stands alone as the world's No 1 fighter, despite the achievements of Ireland's Katie Taylor, an undisputed champion at lightweight.
Salita told Sky Sports: "Claressa is the best female fighter on the planet, not only because of her unmatched ring accomplishments, but also because she is fighting for equal opportunity outside the ring for all the fighters in the world."