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KSI, born Olajide Olayinka Williams Olatunji on 19 June 1993, is a British influencer, musician, and former professional boxer. He is a co-founding member of the YouTube group the Sidemen and the co-founder of Misfits Boxing. He is also a co-owner of several businesses, including Prime Hydration and Lunchly. KSI has served as a judge on Britain's Got Talent since 2026. He was born in London to parents of Yoruba heritage and raised in Watford, where he was privately educated at Berkhamsted School. He created his main YouTube channel KSI, then known as KSIOlajidebt, in 2009, initially gaining a following through commentary videos of the FIFA video game series. His content later expanded to include vlogs and comedic skits. In 2019, he was ranked second by The Sunday Times in its list of most influential online creators in the United Kingdom. In 2021, he appeared in the Europe Entertainment category of Forbes 30 Under 30, and in 2023, Forbes ranked him as the second-top creator. As of January 2025, he has over 44 million subscribers and 14 billion video views across his three active YouTube channels.