AB against India scored a brilliant 57-ball ton at Mumbai's Wankhede stadium.
The right-handed batter's knock helped South Africa defeat India by 214 runs.
Klaasen is the fourth fastest South African to reach the three-figure mark.
He achieved the feat off 54 balls against West Indies in Potchefstroom.
AB smashed a 52-ball hundred against the same opposition in Sydney.
The former Proteas skipper went on to score an unbeaten 162 in the match.
Second on the list is Boucher, who took 44 deliveries to complete his century.
The veteran wicketkeeper achieved the feat against Zimbabwe in Potchefstroom.
AB’s 31-ball hundred is not just the fastest by any South African but the quickest in the world.
His record inning yet again came against the Men in Maroon in Johannesburg.