Real Sociedad de Fútbol, more commonly referred to as Real Sociedad (pronounced [reˈal soθjeˈðað] es ; Royal Society) in English, and Erreala or Reala in Basque, is a Spanish professional sports club in the city of Donostia / San Sebastián, Basque Country, founded on 7 September 1909. It plays its home matches at the Anoeta Stadium.

Real Sociedad won the Liga title in 1980–81 and 1981–82, and finished runner-up in 1979–80, 1987–88, and 2002–03. The club has also won the Copa del Rey three times, in 1909, 1987, and 2020. It contests the Basque derby against rivals Athletic Bilbao. Real Sociedad was a founding member of La Liga in 1929; its longest spell in the top flight was for 40 seasons, from 1967 to 2007.

Traditionally the club followed a policy (similar to that of its rival Athletic) of signing only Basque players, before signing Republic of Ireland forward John Aldridge in 1989. While a strong Basque contingent has been retained among its players, nowadays both non-Basque Spaniards and foreign players are represented at the club. Its youth academy subsequent to the all-Basque era has still been very successful in developing internationally renowned players, such as World Cup winners Xabi Alonso and Antoine Griezmann.

The club has competed in the UEFA Champions League five times. Their first appearance was in the 1981–82 edition, where the club lost in the first round against CSKA Sofia. In the following season, the team reached the semifinals, only to lose narrowly against Hamburger SV. In the 2003–04 season, the club progressed to the round of 16 before losing to Lyon. In the 2013–14 season, the team finished 4th place in the group stage. Their most recent appearance was in the 2023-24 season, where they progressed to the round of 16, losing 4–1 over two legs to PSG.

Aside from football (including a women's team), Real Sociedad also has several sections in athletics, including track and field, field hockey, and basque pelota.