To qualify, new customers must deposit £5 or more, opt in to the promotion via the ‘Offers’ tab and then place a pre-fight bet of a maximum £1 at the normal price for McGregor to win.
The offer is valid until 23:00 BST on August 26, the day of the fight in Las Vegas, Nevada.
Winning wagers placed at the normal price bet will be paid in cash and players’ balances will be credited with free bets on the enhanced price.
Eoin Ryan, head of sportsbook at BetVictor, said: "Mayweather was for a long time pound-for-pound the best boxer in the world, but he is not the force of old. Can McGregor win? You bet and we are giving new customers the opportunity to put their pound on the younger two-weight UFC champion at 100/1.”Source: GMB / iGaming Business