It was Joshua’s first defeat in his career after winning 20 straight victories with 19 coming by the way of knockouts.
Ruiz is now the heavyweight boxing champion and has thrown the division wide open to challengers who want a shot at the titles.
The Mexican’s victory over the Nigerian-born British boxer is regarded as one of the biggest shock in the sports history.
Joshua had a slow start in the match as he went down on the canvass twice to Ruiz in the third round.
After a quiet fourth, Joshua bounced back in fifth round, but at the end of the sixth he looked like he was out of energy, not engaging in the last 30 seconds before the sound of the bell.
Joshua was also knocked down twice more in the seventh round but after the second one, he did not respond to the referee’s instructions and the fight was stopped which handed the underdog a famous victory.
Promoter Eddie Hearn has said that a rematch is likely told hold in either November or December