"There have been serious talks of a rematch ever since Ruiz shocked the world and took AJ's heavyweight title back in June ... and now Eddie Hearn's Matchroom Boxing promotion has confirmed the fight is set for December 7".
According to Mike Coppinger of The Athletic, the fight will take place in an open-air stadium being constructed for the fight.
He then admitted he would be fine with fighting again in the United States, however Riyadh is seen to be a more neutral venue.
England was also touted as a venue, but Hearn suggested that it would be unfair to the champion to travel to Joshua's home country before Saudi Arabia emerged as a strong contender.
"Neutral grounds - LETS GO - Dec. 7th, time to be a 2X - 258MGT", Joshua wrote.
"It's a fight I know I can win, and that's what makes it important, because I know I can win", the 29-year-old told Sky Sports. Joshua will enter the ring with a record of 22-1, while Ruiz will slip between the ropes boasting a record of 33-1. Although the Englishman was a -2000 favorite, it was Ruiz Jr. who pulled off one of the biggest upsets ever as he won by knockout in the seventh round.
The victory gave him the WBO, IBF, IBO, WBA world titles. Now if he could just get by Ruiz Jr.
Joshua activated the rematch clause in his contract soon after the fight was over.
Ruiz Jr vs Joshua II was booked a matter of days after the latter's unsuccessful American debut at Madison Square Garden, though the venue was only announced on Friday evening. His lone loss came at the hands of Joseph Parker back in 2016.
Saudi Arabia has been ramping up its efforts to stage major sporting events, recently hosting British boxer Amir Khan's win over Billy Dib and Callum Smith's triumph over George Groves in September's final of the World Boxing Super Series.
But there was a dispute over where the return clash would land with Ruiz Jr refusing to come to the United Kingdom for a December 14 date at Cardiff's Principality Stadium.