According to BBC Sports, Joshua’s promoter, Matchroom Boxing, made this known in a tweet on its official Twitter page on Friday.
The tweet read: “It’s official! @Andy_destroyer1 vs @anthonyfjoshua 2 will take place in Diriyah, Saudi Arabia on December 7 RuizJoshua2 ClashOnTheDunes COTD.”
A news conference would be held on Monday, 12 August when more details would be revealed.
We reported that Joshua’s world heavyweight title reign and unbeaten record were ended by a stunning defeat to Ruiz Jr in New York in June this year.
Joshua had earlier said that he wants his rematch with Ruiz to take place in Cardiff.
The 29-year-old said: “Ruiz, I’ve seen he’s done a lot of talking about what he wants, but he don’t call the shots in that sense, it’s a team effort.
“It’s fine, I don’t mind fighting him in America, I’ve done it before, and I’d love to fight here because I had no reason to go in the first place. I went there off my own back, so for the rematch now, I would love it to be in Cardiff, however, [if] it’s going to be on neutral ground, Ruiz is the champ, we’ll kind of make some calls as well in that situation.
“But I’m going to battle for it to be in the UK, because it’s my stomping ground. I done one out there, so let’s do the rematch here.
“I think it will be amazing before the year is out and I’ll definitely be having a lovely new years with my family.”
However, Ruiz, who was born in the United States, had ruled out a fight taking place in the United Kingdom.