The bantamweight division, as defined by the unified rules of MMA via the Association of Boxing Commissions (ABC), constitutes fighters who are between 126 and 135 pounds.
Before the New Jersey State Athletic Control Board took charge of MMA regulation in 2001, organizations like the UFC used to refer to its lightweight division as bantamweight (which was introduced back at UFC 26). This, however, was a short-lived period given that the UFC realigned its weight classes by UFC 31, which saw the promotion’s first official lightweight fight at 155 pounds.
