Semi Ajayi (born 9 November 1993) is a professional footballer who plays as a centre-back for Premier League club Hull City and the Nigeria national team. Starting in the Charlton Athletic academy, he signed his first professional contract in 2012, but was poached by Arsenal in September 2013 before he ever made his senior debut for Charlton. While at Arsenal, he scored on his U21 debut and was named as a senior substitute several times, but ultimately moved to Cardiff City in 2015, where he spent much of his time on loan spells with AFC Wimbledon and Crewe Alexandra. After a successful loan at Rotherham United in 2017—where he scored his first goal in a 3–2 defeat to Huddersfield Town—he made the move permanent that July. Born in England to Nigerian parents, he chose to represent Nigeria on the international stage.