Parents are Lilian and Martins. He grew up in Owerri, Nigeria, and attended the NBA Academy in Africa for three years after being discovered as a teenager.
He made the Nigerian national team in 2020 as a 16-year-old and played in the World Cup qualifiers in 2021. Onyenso moved to the U.S. for his senior year of high school and attended Putnam Science Academy in Connecticut for the second half of the year. He helped lead the team to an undefeated record after his integration into the lineup. He was rated as a top-40 recruit in the 2022 class and committed to Kentucky over Oklahoma, Oklahoma State and Tennessee.
Despite high expectations while playing as Oscar Tshiebwe’s backup, Onyenso struggled during his freshman season at Kentucky. He was expected to compete for a starting role in his sophomore season but had foot surgery in the summer and missed the start of the season. He worked his way into starting by the end of the year, but that was the season Kentucky was upset by Oakland in the first round of the NCAA Tournament. John Calipari moved to Arkansas, so Onyenso transferred to Kansas State.
He came off the bench for the Wildcats and played only 11 minutes per game. Then he transferred to Virginia and broke out the way many thought he could. He won ACC All-Defense honors and swatted three shots in just 18 minutes per game as a reserve big. Onyenso is automatically eligible for the 2026 NBA Draft class because he has exhausted his collegiate eligibility.
