The 34-year-old rapper has rocketed to fame since his "Gangnam Style" video - in which he performs his now famous horse-riding dance - became a worldwide hit following its release in July.
Earlier this month the song ousted Jennifer Lopez's dance hit "On the Floor" from second place on YouTube, and on Saturday it overtook Bieber's hit. In the evening, it had racked up 803,761,928 views against 803,658,345 for "Baby".
Psy's song, which is a tribute to an upmarket neighbourhood in Seoul, has topped charts from Britain to Australia and has been name-checked by global notables including US President Barack Obama and UN chief Ban Ki-moon.
It has spawned numerous tribute videos and been imitated by an impressive roster of big names, including Chinese dissident artist Ai Weiwei and London Mayor Boris Johnson.
The quirky star, whose real name is Park Jae-Sang, has won adulation in his homeland for the global hit and was this month awarded one of South Korea's highest cultural honours, the Okgwan Order of Cultural Merit.
South Korea sees popular culture as a potent export force providing international exposure for a country that still feels overlooked in comparison to neighbours China and Japan.
The rapper recently unveiled plans for his next song in an interview with CNN, saying the lyrics would be a mix of English and Korean.