The dance video was posted in late July and started taking off in August and by September, at which point it was being seen 7-10 million times a day, and up to 12 million on Saturdays.
It propelled pop sensation Psy to worldwide fame, reported MTV online.
It has inspired hundreds of parody clips from members of the British army and Thai navy among others.
Youtube's owner Google said the video had been watched seven million to 10 million times a day on average.
It overtook the previous record holder- teen pop star Justin Bieber's music video 'Baby'.
"Psy's success is a great testament to the universal appeal of catchy music and, great equine dance moves," Youtube trends manager Kevin Allocca wrote on the service's blog.
