Weir was born in Cambridge, England, to Scottish parents. She studied with Sir John Tavener whilst at school (North London Collegiate School) and subsequently with Robin Holloway at King's College, Cambridge, graduating in 1976. Her music often draws on sources from medieval history, as well as the traditional stories and music of her parents' homeland, Scotland. Although she has achieved international recognition for her orchestral and chamber works, Weir is best known for her operas and theatrical works. From 1995 to 2000, she was Artistic Director of the Spitalfields Festival in London. She held the post of Composer in Association for the City of Birmingham Symphony Orchestra from 1995 to 1998. She received the Lincoln Center's Stoeger Prize in 1997, the South Bank Show music award in 2001 and the ISM's Distinguished Musician Award in 2010. In 2007, she was the third recipient of The Queen's Medal for Music. She was Visiting Distinguished Research Professor in Composition in Cardiff University from 2006 to 2009.