Ronaldo missed the defeat at Liverpool while on compassionate leave but returned to training on Wednesday, and interim manager Ralf Rangnick confirmed the 37-year-old will be part of the travelling squad to the Emirates.
"Cristiano Ronaldo is available again; he has been training with us," Rangnick told a news conference on Friday.
"Scott McTominay will be back and fit to play; he has trained with us, and the same is true with Raphael Varane. All of the others are still injured, and Paul [Pogba] with the scan, it is very likely he will not play until the end of the season again."
Rangnick and his players head to Arsenal still in the hunt for a place in the top four despite the 4-0 defeat against Liverpool on Tuesday.
United haven't won a league game at the Emirates since December 2017, and Rangnick is hoping for a reaction to the performance at Anfield when his team line up in north London on Saturday morning.
"We only trained yesterday [Thursday] because the day after the game is recovery; yesterday we trained some issues in connection with the game, but the only real training session is on Friday," Rangnick added.
"The players are disappointed, but it is up to them to show their reaction on the pitch tomorrow."