Byrne was born in Hampshire, and grew up amidst many artistic influences. She was raised inStratford-upon-Avon, where theRoyal Shakespeare Company is based. She would later tell an interviewer that her career in theatre design was predestined,[3] and she began by studying architecture with the intention of building sets in theatre.[4][5] She encountered costume design when studying theatre design with theEnglish National Opera. She later said, "I worked in the theatre for quite a few years, doing costume and set design. In England, it's very much both."[5] She also trained with theMotley Theatre Design Course.[6]
Byrne oversaw scenery and costumes for the 1989 comedy playSome Americans Abroad.[7][8] Her work earned her aTony Award nomination forBest Scenic Design.[9] Despite her success, she was unsure if she would focus on set design or costume design. She decided on the latter when she was working on a television project for the BBC'sShakespeare series. Byrne said, "I was assisting a costume designer who was fantastic with fabric. It was with her that I actually thought, 'This is what it's all about. This is what I want to do'".[5]
Byrne's first encounter with period costume dramas began when she was hired to create the costumes for the BBC filmPersuasion. The production was an adaptation of thenovel of the same name byJane Austen, and featuredAmanda Root asAnne Elliot.[3][13] Byrne had also worked with the film's director,Roger Michell, onSome Americans Abroad andThe Buddha of Suburbia.[7][14] For her work inPersuasion, Byrne won the British Academy Television Award for Costume Design.[15] The following year, Byrne created the costumes for the 1996 filmHamlet directed by and starringKenneth Branagh,[10] with whom she had previously worked onLife of Napoleon.[16] She received her first Academy Award nomination forBest Costume Design.[17][18]
In 1998, Byrne served as the costume designer for the feature filmElizabeth, which starredCate Blanchett as thelast Tudor monarch.[19] It featured high production values despite a limited budget.[20] DirectorShekhar Kapur discouraged historical research on Byrne's part, instead favouring clothing that focused on emotion.[21] As a result, Byrne primarily designed costumes emphasising the theatrical rather than the historically accurate.[20] When analysing the film, the scholar Bethany Latham stated that the production's silhouettes were "understated and barely Elizabethan," as they were not meant to distract from the film's plot among viewers.[20] ForElizabeth, Byrne earned her second Academy Award nomination for Best Costume Design.[1]
Byrne oversaw the costumes for the 2004 filmFinding Neverland starringJohnny Depp andKate Winslet.[3] After completing it, Byrne said that when she worked on "a period film, however conceptual a piece it is, I research the period completely so that I absolutely know it. There were photographs from the first production of Peter Pan and of the Llewelyn Davies family".[4] That year,Daily Variety reported that Byrne's "previous two Oscar noms make her a known commodity",[22] and she again garnered a nomination for Best Costume Design at the Academy Awards.[23]
Also in 2004, Byrne designed the costumes for the filmThe Phantom of the Opera.[24] As research, she studied relics of the era such as paintings and original clothing. Her visits to Paris also gave her inspiration. As her ideas developed and were discussed with the filmmakers, they were placed on a "mood board" of visuals for her to reference. She eventually created 300 original costumes for the main characters, and produced at least 2,000 additional costumes for those in the background.[25]
In 2007, Byrne designed the costumes forElizabeth's sequelElizabeth: The Golden Age, also starring Blanchett. As the sequel was set 27 years later, Byrne sought to create costumes for a confident queen "who has found her stride and established her style". Kapur did not feelElizabeth: The Golden Age had to be historically accurate, giving Byrne the freedom to make his film "look very different, much lighter, with a more feminine court".[19] For her costume design work in the film, Byrne was again nominated for the Academy Award, this time winning.[1][26]
Since 2011, much of Byrne's career has focused on films in theMarvel Cinematic Universe. Her first contribution to the franchise,Thor (2011), resulted when she was hired by the film's director, Kenneth Branagh.[3][27] She had also worked with Branagh on previous productions such asHamlet (1996)[28] andSleuth (2007).[29] Byrne took inspiration from theThor comics and the artwork ofJack Kirby, which she described as "amazing".[30] She later said that for Thor's character, "it's all about his arms".[31] AfterThor, Byrne's nextMarvel project was the 2012 filmThe Avengers, where she oversaw a team of over 60 people.[32]
She followedThe Avengers withGuardians of the Galaxy in 2014, which she described as having a "very retro, pulpy feel".[31] As withThor, Byrne found much of her inspiration from the comics.[27] The production's main actor,Chris Pratt, was hired before he had lost enough body weight, forcing Byrne to anticipate what his physical form would become.[27] When describing Pratt's characterStar-Lord inGuardians of the Galaxy, Byrne said he "was all about the swagger, but without vanity" and designed a red jacket for him that was heavily treated cotton, though it looked like real leather.[31] Her next project,Avengers: Age of Ultron, arrived in cinemas in May 2015.[31]
Byrne is the costume designer for the 2016 Marvel filmDoctor Strange starringBenedict Cumberbatch,[33] which began shooting in November 2015 atPinewood-Shepperton studios in the UK.[34][35] For Strange's famousCloak of Levitation, Byrne estimated that twelve different versions were completed by a team of designers. She sought to incorporate subtle details while avoiding making it "over-embellish[ed] and decorative".[36]