Olajide Olayinka Williams “JJ” Olatunji (/ɒləˈdʒiːdeɪ ɒləˈtundʒiː/, oh-lah-JEE-day oh-lah-TUHN-jee; born 19 June 1993), better known as KSI, is a British YouTuber, actor, rapper, singer, songwriter, and boxer. He is also a co-founder and member of the British YouTube group known as the Sidemen.