Oluwasemilogo Adesewo Ibidapo "Semi" Ajayi MON (born 9 November 1993) is a professional footballer who plays as a centre-back for EFL Championship club West Bromwich Albion.

[3] Born to Nigerian parents, Ajayi began his football career as a youth product of the Charlton Athletic academy.

[5] Shortly after, he made his Dartford debut, in a 4–0 win over Kingstonian in the FA Trophy[6] and then scored his first goal for the side, in a 3–2 loss against Tamworth.

[8] After returning to Charlton Athletic, Ajayi played for the reserve side for the rest of the season and helped them win the Professional Development League 2.

[11] Ajayi made his Arsenal U21 debut as a trialist against Blackburn Rovers on 30 August 2013, scoring with a header, in a 3–0 win.

[20] After impressing in his first couple of games, he was keen to extend his loan spell at AFC Wimbledon for more first team opportunities.

[25] On 13 February 2016, with chances of further loan extension reported as slim,[26] he set up a goal for Brad Inman in a 1–1 draw against Walsall.

[29] On 30 January 2017, Ajayi signed a loan deal until the end of the 2016–17 season with fellow Championship strugglers Rotherham United.

[38] On 20 July 2019, Ajayi signed for West Bromwich Albion for an undisclosed fee, agreeing a four-year contract with the club.