Herbert Jansch (born 3 November 1943), known as Bert Jansch, is a Scottish folk musician and founding member of the band Pentangle. He was born in Glasgow and, in the 1960s, he was heavily influenced by the guitarist Davey Graham and folk singers such as Anne Briggs. He is best known as an innovative and accomplished acoustic guitarist but is also a singer and songwriter.

He has recorded at least 25 albums and has toured extensively starting in the 1960s and continuing into the 21st century. His work has influenced such artists as Johnny Marr, Bernard Butler, Jimmy Page, Ian Anderson, Nick Drake, Donovan and Neil Young, and earned him a Lifetime Achievement Award at the 2001 BBC Folk Awards.

Bert Jansch was born at Stobhill Hospital, Glasgow in 1943, but brought up in Edinburgh, where he attended Pennywell Primary School and Ainsley Park Secondary School. As a teenager, he acquired a guitar and started visiting a local folk club run by Roy Guest. There, he met Archie Fisher and Jill Doyle, who introduced him to the music of Big Bill Broonzy, Pete Seeger, Brownie McGhee and Woody Guthrie. He also met and shared a flat with Robin Williamson, with whom he travelled to London in 1963.

After a stint as a nurseryman, Jansch became a full-time musician and spent two years playing one-night stands in British folk clubs. This was a musical apprenticeship which exposed him to a range of influences, including Martin Carthy and Ian Campbell, but especially Anne Briggs, from whom he learnt some of the songs  that would later feature strongly in his recording career.

Between 1963 and 1965, he travelled around Europe and beyond, hitch-hiking from place to place and living on earnings from busking and casual musical performances in bars and cafes. Before leaving Glasgow, he married a 16-year-old girl called Lynda Campbell: a marriage of convenience, which allowed her to travel with him although she was too young to have her own passport. They split up after a few months and Jansch was eventually repatriated to Britain after catching dysentery in Tangiers.

Through the development of Pentangle, Jansch played a number of instruments: banjo, Appalachian dulcimer, recorder and concertina—on rare occasions he has even been known to play electric guitar. However, it is his acoustic guitar playing that sets him apart from other folk musicians.

Jansch’s first instrument was a Zenith which was marketed as the "Lonnie Donegan guitar" and which he played in the folk clubs in the early 1960s. His first album was reputedly recorded using a Martin 002 borrowed from Martin Carthy. Pictures of Jansch in the middle 1960s show him playing a variety of models, including Martin and Epiphone guitars. He had a guitar hand-built by John Bailey, which was used for most of the Pentangle recordings but was eventually stolen. He then had a contract with Yamaha, who provided him with an FG1500 which he is still playing, along with a Yamaha LL11 1970s jumbo guitar. Jansch’s relationship with Yamaha continues and they presented him with an acoustic guitar with gold trim and abalone inlay for his 60th birthday although, valued at about £3000, Jansch is quoted as saying that it is too good for stage use.