The club was founded in 1903, under the name of Athletic Club de Madrid. Its founders, three Basque students living in Madrid, considered the club a youth branch of Athletic Bilbao. Following the end of the Spain civil war in 1939, Athletic was merged with a Zaragoza football club founded the same year, Aviación Nacional. The new club was named Athletic Aviación de Madrid. The merger quickly proved successful, as Athletic Aviación managed to win its first La Liga in 1940 and defend the title in 1941. In 1947, the club changed its name for the final time; it was henceforth known by its current name of Club Atlético de Madrid. Atlético's home kit is red and white vertical striped shirts, with blue shorts, and blue and red socks. This combination has been used since 1911. Throughout their history the club has been known by a number of nicknames, including Los Colchoneros.
Diego Simeone's appointment as head coach in 2011 saw the club return to its former paths of glory without really big stars, but with the idea of collectivism. Under his leadership, the club won a Europa League in 2012, and followed it up with a Copa del Rey in 2013 and its tenth La Liga in 2014. After the team's victory in the UEFA Europa League and UEFA Super Cup in 2018, Simeone became the most successful manager in the club's history. The club's missing trophy is that of the Champions League. Athlético has been close to win it, being runners-up in 2013–14 and 2015–16 plus reaching the semi-finals in 2016–17.