Sport Lisboa e Benfica (Portuguese pronunciation: [sɨˈpɔɾ liʒˈβo.ɐ i βɐ̃jˈfikɐ] (listen)), commonly known as Benfica, is a professional football club based in Lisbon, Portugal, that competes in the Primeira Liga, the top flight of Portuguese football.

Founded on 28 February 1904 as Sport Lisboa, Benfica is one of the "Big Three" clubs in Portugal that have never been relegated from Primeira Liga, along with rivals Sporting CP and FC Porto. Benfica are nicknamed As Águias (The Eagles), for the symbol atop the club's crest, and Os Encarnados (The Reds), for the shirt colour. Since 2003, their home ground has been the Estádio da Luz, which replaced the larger, original one, built in 1954. Benfica is the most supported Portuguese club and the European club with the highest percentage of supporters in its own country, having over 250,000 members and an estimated 14 million supporters worldwide. The club's anthem, "Ser Benfiquista", refers to Benfica supporters, who are called benfiquistas. "E pluribus unum" is the club motto; Águia Vitória, the mascot.

Benfica is honoured with the Portuguese Orders of Christ, of Prince Henry, and of Merit. Competitively, with 83 major trophies won – 84 when including the Latin Cup – Benfica is the most decorated club in Portugal. They have won 80 domestic trophies: a record 37 Portuguese League (Primeira Liga) titles, a record 26 Portuguese Cup (Taça de Portugal), a record 7 Portuguese

League Cup (Taça da Liga), 8 Portuguese Super Cup (Supertaça Cândido de Oliveira) and 3 Campeonato de Portugal. Internationally, they won back-to-back European Cups in 1961 and 1962 – a unique feat in Portuguese football – and were runners-up at the Intercontinental Cup in 1961 and '62, at the European Cup in 1963, '65, '68, '88 and '90, and at the UEFA Cup/Europa League in 1983, 2013 and '14. Benfica's ten European finals are a domestic record and ranked seventh all-time among UEFA clubs in 2014.Benfica was voted 12th in FIFA Club of the Century and ranked 9th in the IFFHS Top 200 European clubs of the 20th century. In UEFA, Benfica ranks 8th in the all-time club ranking and was 24th in the club coefficient rankings at the end of the 2020–21 season. Currently, Benfica have the second most participations in the European Cup/UEFA Champions League (41), tournament in which they hold the overall record for the biggest aggregate win, achieved in 1965–66. Moreover, Benfica hold the European record for the most consecutive wins in domestic league and the record for the longest unbeaten run in Primeira Liga, where they became the first undefeated champions, in 1972–73.