Born on 21 March 2003 in Spain, Mateo Mejía began his development at the youth academy of Zaragoza before making the move to England in 2019, joining Manchester United's academy at the age of sixteen. That early switch to one of European football's most prominent setups underlined the level of promise coaches saw in him from a young age.
Mejía made his senior debut on 22 August 2023, starting for Manchester United's under-21 side in a 1–1 draw against Stockport County in the EFL Trophy — a match United won 6–4 on penalties. He signed a new contract with the club in June 2023, demonstrating their continued belief in his development. In January 2024, he moved on loan to Sevilla Atlético in Spain's Segunda Federación, and notably came off the bench on 29 September 2024 in a 1–1 away draw against Athletic Bilbao, marking his first-team debut at that level.
A direct and mobile winger with an eye for goal, Mejía suits the wide attacking roles where he can run in behind defences or cut inside. In July 2025, he joined Burgos CF in the Segunda División on a three-year deal, a move that represents a significant step up in his senior club career.
Although born in Spain, Mejía is eligible to represent Colombia internationally through his parents. He made his debut for the Colombia under-20 side in December 2022 in a two-legged friendly against Peru under-20, and international development at youth level remains part of his broader ambitions.