Olajide Olayinka Williams "JJ" Olatunji (, oh-lah-JEE-day oh-lah-TUHN-jee; born 19 June 1993), better known as KSI, is an English YouTuber and rapper. He is a member and co-founder of the British YouTube group known as the Sidemen, which has a combined audience of over 53 million subscribers.In 2009, KSI registered his YouTube account under the name KSIOlajideBT. KSI built his following from posting gaming–commentary videos of the FIFA video game series, although as his following has grown, his content has diversified to include more vlog and comedy style videos. As of February 2020, the channel has received over 21 million subscribers and over 5 billion video views, ranking as the third-most subscribed music channel in the UK, and placing him among the top 30 most subscribed music artists on the platform.Having written and produced comedy–rap songs in his early YouTube career, KSI has since recorded more purist works, topping both the UK R&B Albums and Singles charts. He reached the top 10 of the UK Singles Chart in 2019 with his single, "Down Like That", which featured S-X, Rick Ross and Lil Baby. As an actor, KSI featured in the British comedy film Laid in America (2016), and was the subject of Can't Lose (2018), a documentary film following the build-up to his first amateur boxing fight.
KSI has been involved in three high-profile boxing bouts; the first two were amateur white-collar events, and the third was a professional bout. The first, against British YouTuber Joe Weller, was won by KSI via technical knockout, and drew a live online audience of over 1.6 million. The second fight, versus American YouTuber Logan Paul, ended in a majority draw; The subsequent rematch was KSI's professional boxing debut, which he won via split decision.