Born on 6 October 1998 in Bristol, England, Kelly is a central defender who can also be deployed as a left-back. Rising through the Bristol City youth ranks, he made his first team debut in 2017, impressing with his combination of physical strength and technical qualities. In 2019 he moved to Bournemouth, where he remained until 2024, playing 141 games and scoring three goals.

He then joined Newcastle in the summer, featuring in a total of 14 matches for the Magpies. Since Jan 2025 he's a Juventus player