South Korean rapper PSY's Gangnam Style has become YouTube's most watched video of all time.

Gangnam Style was released on July 15.

The music video has been viewed over 810 million times on YouTube, surpassing the previous title holder, Justin Bieber's Baby earlier today.

Bieber fans did not let the Canadian popstar go down without a fight.

They took to Twitter in a campaign to get Baby to a billion views, with some reportedly playing the song in dozens of browser tabs at once.

PSY's dance moves in the video have seen him appear on The Today Show and The Ellen DeGeneres Show and spawned many parodies.