The 2017–18 season was Sport Lisboa e Benfica's 114th season in existence and the club's 84th consecutive season in the top flight of Portuguese football. It started on 5 August 2017 with Benfica's victory in the Supertaça Cândido de Oliveira and concluded on 13 May 2018. Benfica played in the Primeira Liga as four-time defending champions for the first time in their history and finished second. Benfica also entered the Taça de Portugal as title holders but were eliminated in the fifth round. Moreover, they were eliminated in the third round of the Taça da Liga.