Liege & Lief is the fourth album by the British folk rock band Fairport Convention. It is the third album the group released in the UK during 1969, all of which prominently feature Sandy Denny as lead female vocalist (Denny did not appear on the group's 1968 debut album), as well as the first to feature future long-serving personnel Dave Swarbrick and Dave Mattacks on violin/mandolin and drums, respectively, as full band members (Swarbrick had previously guested on Unhalfbricking). It is also the first Fairport album on which all songs are either adapted (freely) from traditional British and Celtic folk material (for example "Matty Groves", "Tam Lin"), or else are original compositions (such as "Come All Ye", "Crazy Man Michael") written and performed in a similar style. Although Denny and founding bass player Ashley Hutchings quit the band before the album's release, Fairport Convention has continued to the present day to make music strongly based within the British folk rock idiom, and are still the band most prominently associated with it.

The album was moderately successful, peaking at number 17 on the UK Albums Chart during a 15-week run. It is often credited, though the claim is sometimes disputed, as the first major "British folk rock" album (this term is not to be confused with American-style folk rock, which had first achieved mainstream popularity on both sides of the Atlantic with the Byrds' early work several years prior). The popularity of Liege & Lief did a great deal to establish the new style commercially and artistically as a distinct genre. In an audience vote at the BBC Radio 2 Folk Awards in 2006, the album was voted "Most Influential Folk Album of All Time". It was voted number 254 in the third edition of Colin Larkin's All Time Top 1000 Albums (2000).