That third round.

KING DETHRONED: Anthony Joshua KO’d in one of boxing’s greatest ever upsets

In what will go down as one of the biggest upsets in boxing history, Anthony Joshua lost his IBF, WBA Super and WBO, and IBO heavyweight titles to Andy Ruiz Jr at a packed out Madison Square Garden on Sunday (AEST).

A huge underdog, Ruiz Jr. was dropped in the third, before getting back to his feet and flooring the British superstar twice before the end of the round.

Ruiz Jr. finished the job in the seventh.

Watch the wild third round below!