Harris suffered the injury on Monday during a game against Yale.
This is Harris' second ACL injury in the past 13 months. He tore the ACL in his left knee as a high school senior in December 2018 and missed the first eight games of this season while he recovered from that injury.
"This is one of the most heartbreaking injuries one of my teams has ever dealt with," head coach Roy Williams said. "Anthony is such a great kid and his teammates and coaches have all seen the countless hours he put in to come back from the knee injury he suffered in high school. The impact on our locker room after the Yale game was devastating. Everyone associated with our program hurts for Anthony and his family. But we will rally around him and support him every step of the way. I know he will work unbelievably hard to get back on the floor."
Harris, a 6-foot-4 guard from Virginia, averaged 6.8 points in five games this season. He has played a key reserve role since Cole Anthony was injured in early December, coming off the bench and providing scoring punch. Harris scored a season-high 14 points in a win over UCLA. He was an ESPN 100 prospect in the 2019 class.
It's the latest injury for a North Carolina team that has struggled during the first two months of the season. The Tar Heels are still without star guard and potential top-five pick Anthony, who is expected to miss at least another two to four weeks after undergoing a procedure on his right knee. Only four players on Carolina's roster have played all 13 games this season.
North Carolina (8-5) host Georgia Tech on Saturday.