Mario Fernández Cuesta (born 30 April 1988) is a Spanish professional footballer who plays for FC Cartagena as a goalkeeper.
Born in Santander, Cantabria, Fernández was a product of Racing de Santander's youth ranks, and was promoted to the main squad for the 2009–10 season, acting as backup to established Toño and Fabio Coltorti. Benefitting from a serious injury to the former, he began being picked for some matches while also representing the reserves in the third division.
On 6 January 2010, Fernández made his official debut for Racing's first team, in a 3–2 away win against AD Alcorcón for the Copa del Rey– he also featured in the second leg (0–0 draw), adding another two appearances in the tournament as his team reached the semi-finals. As the Cantabrians were already safe from relegation, and longtime first-choice Toño was suspended, he made his La Liga debut on 15 May 2011, earning Man of the match accolades in a 1–2 loss at Sporting de Gijón.