On 26 April 1903, a group of students founded Atlético Madrid. They have since become one of Spain's most successful clubs, winning the league and the Copa del Rey ten times each.
The initial group of students consisted of Basques who were Athletic Bilbao and who considered the new club to be a Bilbao youth affiliate. They called the new club Athletic Club de Madrid and even adopted Bilbao's blue and white stripes, though they changed to their current red and white stripes by 1911 (reportedly attributable to their purchase that year of shirts from Southampton FC).
They joined La Liga in 1928, but were relegated to the Segunda División two years later. A few ups and downs later, and a merger with Zaragoza's Aviación Nacional, they returned to the top flight for the 1939-40 season and proceeded to win two straight titles. They won two more in 1950 and 1951 under manager Helenio Herrera. They have since added five more, including their most recent one in 2014. They won their tenth Copa del Rey in 2013.
Atlético have also enjoyed success in Europe. They won the Cup Winners' Cup over Fiorentina in 1962 and reached the European Cup final in 1974 (where they lost to Bayern Munich). They were the Champions League runners up in 2014 and 2016, losing both times to Real Madrid. In 2010, they won the Europa League final over Fulham, then claimed the UEFA Supercup by beating Inter 2-0.