Okongwu was born Dec. 11, 2000 in Los Angeles, California. He is the son of Nigerian parents Kate and Mike Okongwu. The 6-foot-9 forward attended Chino Hills High School in Chino Hills, California and started on the varsity basketball team as a freshman. Also as a freshman, he was teammates with the three Ball brothers -- Lonzo, LiAngelo and LaMelo. That season, the team secured a 35-0 record and won the California Interscholastic Federation Open Division State Title. Okongwu shared MaxPreps National Freshman of the Year honors with LaMelo Ball. Later, as a junior, Okongwu earned the California Mr. Basketball title after averaging 28 points, 14 rebounds and four blocks per game. He repeated the next season, becoming just the fifth player ever to do so. In college, Okongwu played one season at USC, earning First-team All-Pac-12 honors before declaring for the 2020 NBA Draft. He wears jersey No. 21 to honor his late brother.