Sport Lisboa e Benfica "B" (Portuguese pronunciation: [sɨˈpɔɾ liʒˈβoɐ i βɐ̃jˈfikɐ be], commonly known as Benfica B, is a Portuguese professional football team based in Seixal. Founded in 1999, dissolved in 2006, and restarted in 2012, it is the reserve team of Portuguese club S.L. Benfica. They play in the Liga Portugal 2, holding home matches at Benfica Campus' main pitch.

During the 2012–13 season, Benfica B played home matches at the Estádio da Luz until February, when they moved to Estádio da Tapadinha to prevent excessive wear of the stadium's grass. In 2013–14, they moved permanently to their own training ground, capable of receiving professional league matches.

As a reserve team, Benfica B cannot play in the same division as the club's main team, thus being ineligible for promotion to the Primeira Liga. Moreover, they cannot enter domestic cup competitions such as the Taça de Portugal and Taça da Liga. Since 2018–19, Benfica have an under-23 team playing in Liga Revelação.