Callum John Smith is a British professional boxer. He has held the World Boxing Organization (WBO) interim light-heavyweight title since February 2025. Previously, he held the World Boxing Association (WBA) (Super version) and Ring magazine super-middleweight titles from 2018 to 2020. Both of his titles were won during the World Boxing Super Series tournament, in which he won the Muhammad Ali Trophy. At regional level, he has held multiple super-middleweight championships, including the British and European titles between 2015 and 2017. As an amateur, he won a silver medal at the 2010 Commonwealth Games. He is the youngest of the Smith brothers, Paul, Stephen, and Liam, all of whom are professional boxers.