Tomás Mejías Osorio (born 30 January 1989) is a Spanish professional footballer who plays as a goalkeeper for Turkish club Ankaraspor.
Mejías was born in Madrid. In 2001, aged 12, he joined local Real Madrid's youth academy from neighbouring amateurs CD Coslada. He made his professional debut in the 2007–08 season, playing five games for the reserves in Segunda División B.
As first-team manager José Mourinho decided to rest Iker Casillas, Mejías was selected for a La Liga home match against Getafe CF on 10 May 2011. He replaced another club youth graduate, Antonio Adán, for the last ten minutes of a 4–0 home win.
Mejías was selected in a 20-man squad for the first match of the 2011–12 campaign, at Real Zaragoza, being awarded the #52 jersey, but eventually did not make the bench. He contributed with 26 appearances in the following year, as the B's retained their Segunda División status.
On 11 February 2014, Mejías joined English Championship side Middlesbrough on loan until the end of the season. He made his debut for his new team on 1 March, in a 0–1 away loss against Sheffield Wednesday. It was his only appearance during the time of his loan, as he dislocated a finger in training and was sidelined for the rest of the campaign.
On 4 July 2014, Boro made the deal permanent and signed Mejías to a two-year contract. On 28 October of the following year, he saved from Wayne Rooney and Ashley Young as his team won in a penalty shootout away to Manchester United in the fourth round of the League Cup, also keeping a clean sheet for 120 minutes.