Harris was born in Dallas, Texas, the son of Karlin Kennedy and Erion Harris, both of whom played basketball at SMU, and has two younger brothers and a sister. His mother gave birth to him at the age of 19 but returned to the floor at SMU for her junior season and graduated as the Mustangs' all-time leader in points, rebounds, blocks and field-goal percentage. Harris grew up in Duncanville and played basketball, football, and baseball. He gave up football after an injury in middle school, after which he trained with his father to become a high-level basketball player. His father formed the travel team Dallas Heroes around his son in middle school. He attended Duncanville High School and grew to 6'3 as a sophomore. As a junior, he averaged 15 points, 4 rebounds, and 2 assists per game and was named the District 8-6A Offensive Player of the Year. He suffered a broken vertebrae during an AAU event, forcing him to miss half of his senior season. Nevertheless, Harris was again named District 8-6A Offensive Player of the Year as a senior. He averaged 23 points, 7 rebounds, 4 assists and 2 steals per game as a senior and shot 55 percent from the field and 45 percent on three-point attempts. In a game against Cedar Hill High School, Harris scored a career-high 44 points. He was rated as the 16th best player and the ninth best guard in Texas in his class by Rivals.com. Harris spurned offers from Indiana and Kansas State to sign with Louisiana Tech.
College career
Harris began his collegiate career at Louisiana Tech. As a true freshman, he averaged 10.9 points and 3.1 rebounds per game and was named to the Conference USA All-Freshman team. As a sophomore, Harris led the Bulldogs in scoring with 15.3 points per game while also averaging 4.5 rebounds, 2.5 assists and 1.1 steals per game, shooting 44.4 percent from behind the arc. He decided to transfer after 11 games. In January 2018, he signed with Nevada over offers from Oklahoma State, Tulsa and Stephen F. Austin. Harris chose the Wolf Pack after attending a game against Boise State after being impressed by coach Eric Musselman and welcoming fans and sat out the 2018-19 season as a redshirt, during which Nevada finished 29-5. After his redshirt season, coach Musselman left for Arkansas, and Harris entered the transfer portal again the day before the school hired Steve Alford. Despite receiving interest from Gonzaga and SMU, Harris decided to stay at Nevada. He missed his second game with his new team with a foot injury and struggled in a game against USC, finishing 3-of-19 with nine points. During an eight game stretch in January 2020, Harris averaged 27 points, 5.4 rebounds and 4.4 assists per game. On February 11, he was named Oscar Robertson National Player of the Week by the U.S. Basketball Writers Association after scoring a career-high 38 points against Air Force and 32 points against San Diego State. He had 29 points, a career-high 14 rebounds, five assists, and two steals in a 82-79 overtime win against UNLV on February 12, becoming the 11th Nevada player to tally at least 20 points, 10 rebounds and five assists in a game. Harris is the first Nevada player since Nick Fazekas in 2006 to have four or more 30-point games in a season. At the conclusion of the regular season, Harris was named to the First Team All-Mountain West Conference and conference newcomer of the year. He averaged 21.7 points and 6.5 rebounds per game.
