In a match between Brisbane Heat and Melbourne Stars, Harris struck 13 boundaries and six sixes during her knock.
Grace reached the unbeaten score of 101 from just 42 deliveries, surpassing Sydney Sixers’ right-handed batswoman Ashleigh Gardner’s previous record of 114 runs off just 52 balls.
Her blistering inning helped her team achieving a thumping 10-wicket victory over Melbourne Stars.
West Indies batswoman Deandra Dottin holds the record for hitting the fastest hundred. In 2010, she struck a century in just 38 balls in the 2010 T20 World Cup.