Joshua stuck to his back-foot game plan to pick off a clear 118-110 (twice), 119-109 verdict in a bout that boasted little of the five-knockdown drama which saw him lose to Ruiz in June.
In a bout which had been threatened with delay by a rare desert rain-storm moments before they took to the ring, the champion banked almost entirely on landing another big left money-shot.
Second time round, a more composed and disciplined Joshua for the most part resisted the urge to join Ruiz in battle, and there was no doubt as to the clear winner once the bell ended the final round.
Confirmation of Joshua’s win was greeted with roars of approval from a capacity 16,000 crowd in the purpose-built venue in the ancient Saudi capital, which was hosting a major title fight for the first time.
Speaking in the ring, Joshua said: “This is about bossing. I’m used to knocking guys out and the last time I realised, hang on a minute, I hurt the man and I got caught coming in, and there were no excuses.
“I said I was going to correct myself and come again. I’m hungry and humble in defeat and I want to remain hungry in victory.”
An extraordinary promotion beset by accusations by human rights organisations of so-called ‘sportswashing’ saw Joshua pocket a record £60million purse with the promise of more Middle East fights to come.
As if the bout needed any additional hype, opinion had been split over its outcome, with many believing Ruiz simply had to land another of his crude left hands to take the titles back home to the US-Mexican border.
And, while the atmosphere could not match those summoned in British football stadiums, there was certainly a liveliness amongst a local audience that eclipsed the routine atmosphere of most Las Vegas casinos.
Joshua rewarded them with a performance which seldom deviated from the script as he skated out of trouble against a much heavier opponent whose extra luggage clearly minimised his chances of retaining his title.
But men were cut around their left eyes in the first two rounds and it took until the fourth round for the bout to burst into life with an exchange on the bell which served as a timely reminder of the danger posed by the champion.
Racking up the rounds on the scorecards, Joshua nevertheless showed an occasional propensity to switch off, allowing Ruiz rare and tantalising glimpses of a repeat success.
Every time Joshua was drawn in close the momentum swung in Ruiz’s favour and a left-right combination in the ninth served as another example as the Mexican instantly responded by dragging the challenger into danger.
Ruiz showed his frustration in the bout’s final seconds as he stood in the centre of the ring beckoning Joshua to engage, and when the final bell sounded the Briton raised his arms to vindicate his emphatic victory.