Here is a comprehensive summary of the Wikipedia article about Sport Lisboa e Benfica:
Sport Lisboa e Benfica, widely known as Benfica, is a celebrated Portuguese football club founded in Lisbon on February 28, 1904. As one of Portugal's "Big Three" clubs, they are famously nicknamed "As Águias" (The Eagles) and play at the iconic Estádio da Luz since 2003.
Benfica holds the distinction of being the world's largest sports club by membership, boasting 400,000 members by February 2025, alongside an estimated 14 million supporters worldwide, making them the most supported club in Portugal. They are the most decorated club in Portugal with 88 major trophies, including a record 38 Primeira Liga titles and 26 Taça de Portugal wins.
Internationally, Benfica achieved the unique feat of winning back-to-back European Cups in 1961 and 1962, in addition to a Latin Cup in 1950, and hold a national record of ten European finals appearances. The club's historical prominence is further cemented by being voted 12th in the FIFA Club of the Century and holding European records such as 29 consecutive domestic league wins, becoming the first undefeated champions in the 1972–73 season.