S.L. Benfica 2015, Benfica reported to have 246,401 members; however, after a scheduled renumbering by the club in August 2015, the number decreased to 156,916. In April 2017, Benfica reported they had a total of 184,264 members by 31 December 2016. Benfica has rivalries with Sporting CP and FC Porto, with whom it forms the "Big Three": Portugal's most decorated clubs. None of them have been relegated from the Portuguese league since its establishment in 1934. As Lisbon-based clubs, Benfica and Sporting have shared a rivalry for over a century; it all started in 1907 when eight prominent Benfica players defected to
1970–71 S.L. Benfica season put Sporting and Benfica level on points. Benfica closed March with an away win over Leixões, with Porto losing and dropping out of race. This left Benfica and Sporting with a three–point lead and three match-days to go. On 4 April, Benfica beat Vitória de Setúbal at home and for the first time headed the league isolated, with a two-point lead. Sporting had lost with Porto. Three weeks later, Benfica confirmed their league title with an away win over Varzim. It was their 18th league title. They finished the Primeira Divisão with a 5–1 victory over Académica, ending the campaign