Weir was born in Cambridge, England, to Scottish parents. She trained with John Tavener while still 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 native Scotland. She is best known for her operas and theatrical works, although she has also achieved international recognition for her orchestral and chamber works. From 1995 to 2000, she was the 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 and in 2001 the South Bank Show music award. In 2007, Weir was the third recipient of the The Queen's Medal for Music.
Weir's musical language is fairly conservative in its mechanic, with a "knack of making simple musical ideas appear freshly mysterious." Her operatic musical writing is sometimes compared to Britten's, and has been described as alternating "twee rhyming couplets and inert blank verse". Her first stage work, The Black Spider, was a one act opera which premiered in Canterbury in 1985 loosely based on the short novel of the same name by Jeremias Gotthelf. She has subsequently written one more "micro-operas", three full length operas, and an opera for television. In 1987, her first half length opera, A Night at the Chinese Opera, premiered at Kent Opera. This was followed by her other two full length operas The Vanishing Bridegroom (1990) and Blond Eckbert (1994), the latter commissioned by the English National Opera. In 2005 her opera Armida, an opera for television, premiered on Channel Four in the United Kingdom). The work was made in co-operation with Margaret Williams. Weir's commissioned works most notably include woman.life.song (2000) for Jessye Norman and We are Shadows (1999) for Simon Rattle. In January 2008, Weir was the focus of the BBC's annual composer weekend at the Barbican Centre in London. The four days of programmes ended with a first performance of her new commission, CONCRETE, a choral motet. The subject of this piece was inspired by the Barbican building itself - she describes it as ‘an imaginary excavation of the Barbican Centre, burrowing through 2,500 years of historical rubble’.
- The Black Spider (6 March 1985, Canterbury)
- The Consolations of Scholarship (5 May 1985, Durham)
- A Night at the Chinese Opera (8 July 1987, Cheltenham)
- The Vanishing Bridegroom (1990, Glasgow)
- Blond Eckbert (20 April 1994, London)
- Armida (2005, television broadcast for Channel Four in the United Kingdom)
- Miss Fortune (Achterbahn) (21 July 2011, Bregenzer Festspiele, in a co-production with the Royal Opera, Covent Garden, London; English language with German surtitles)
Miss Fortune (Achterbahn) 
On 21 July 2011, her first opera for 17 years, Miss Fortune (Achterbahn), premiered at the Bregenz Festival in Austria. The opera reworks a Sicilian folktale as a contemporary parable. Gerhard R. Koch, writing in the Frankfurter Allgemeine newspaper on 25 July, had these observations:
- The music of Judith Weir, who also wrote the libretto for her opera, is neither avant-garde nor experimental but has a highly distilled folkloric style with cantabile voices similar to that of Britten without becoming retrospective. Tonality and atonality are not applied in a strictly antithetical manner, therefore the ideas of the American minimalists Reich and Riley are very present. This music has colour and a rhythmic pulse; it creates characteristic sounds without losing itself in descriptive patterns. B
A co-production with the Royal Opera House, Miss Fortune moved to London in March 2012, garnering at least two negative reviews. Edward Seckerson in The Independent wrote of "Miss Fortune in name and deed" and described the opera as "silly and naive" and "a waste of talent and resources," with a libretto that "vacillates between the banal and the unintentionally comedic (or is that irony?), full of truisms and clunky metaphors" and "about as streetwise as a visitor from Venus." Andrew Clements wrote in The Guardian of "a long two hours in the opera house" with scenes that "follow like cartoonish tableaux, without real characterisation, or confrontation, and without suggesting a dramatic shape."
Other key works 
- King Harald’s Saga (1979; soprano, singing eight roles)
- Piano Concerto (1997)
- We Are Shadows (1999; choir, orchestra)
- woman.life.song (2000; premiered at Carnegie Hall and performed by Jessye Norman)
- The welcome arrival of rain (2001; orchestra)
- Tiger Under the Table (2002; chamber ensemble)
- Piano Trio Two (2003-200])
- Judith Weir: Discography
- A Night at the Chinese Opera - NMC D060
- King Harald’s Saga - Cala CACD88040
- Piano Concerto; Distance and Enchantment; various other chamber works - NMC D090
- Blond Eckbert Nicholas Folwell (baritone), Blond Eckbert; Anne-Marie Owens (mezzo soprano), Berthe; Christopher Ventris (tenor), Walther / Hugo / An Old Woman; Nerys Jones (soprano), A bird; Chorus and Orchestra of English National Opera; Siân Edwards (conductor) Collins Classics: CD14612 / NMC: NMC D106
- On Buying a Horse: The songs of Judith Weir On Buying a Horse; Ox Mountain Was Covered by Trees; Songs from the Exotic; Scotch Minstrelsy; The Voice of Desire; A Spanish Liederbooklet; King Harald's Saga; Ständchen. Susan Bickley] (mezzo soprano), Andrew Kennedy (tenor), Ailish Tynan (soprano), Ian Burnside (piano) Signum SIGCD087
- Morrison, Richard (18 January 2008). "The wonderful Judith Weir - With a Barbican weekend devoted to her music, the composer Judith Weir is being feted as never before". The Times & Sunday Times Archives (London: Times Newspapers). Retrieved 31 January 2011.
- Clements, Andrew (13 March 2012). "Miss Fortune – review". The Guardian (London).
- Opera Glass
- Chester Novello
- Seckerson, Edward (13 March 2012). "Miss Fortune, Royal Opera House". The Independent (London).
- Warrack, John and West, Ewan (1992), The Oxford Dictionary of Opera, 782 pages, ISBN 0-19-869164-5