Olajide Olayinka Williams "JJ" Olatunji (, oh-lah-JEE-day oh-lah-TUHN-jee; born 19 June 1993), known professionally as KSI, is a British YouTuber, internet personality and rapper known for his YouTube video content. KSI is a member and co-founder of the entertainment collective known as the Sidemen, alongside six other British YouTubers, producing online videos and merchandise to 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 in include more vlog and comedy style videos. As of October 2019, the channel has received over 20 million subscribers and 4 billion video views, ranking as the sixth-most subscribed and nineteenth-most viewed channel from the United Kingdom, and placing him among the top 120 most subscribed channels on the site.Having written and produced comedy–rap songs in his early YouTube career, KSI released his more purist debut extended play, Keep Up, in 2016, reaching number one on the UK R&B Albums Chart. After releasing three more extended plays and singles, KSI released a collaborative album with Randolph, titled New Age, in 2019. The same year, KSI signed a record deal with RBC Records; his first single under the new record label, "Down Like That", featured British artist S-X and American rappers Rick Ross and Lil Baby and peaked at number 10 on the UK Singles Chart. 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. With a live online audience of over 1.6 million, the fight was described as the largest white-collar boxing event in history. The second fight, versus American YouTuber Logan Paul, ended in a majority draw and was labelled 'the largest event in YouTube history'. The subsequent rematch was KSI's professional boxing debut, which he won via split decision.