Björk Guðmundsdóttir OTF (/bjɜːrk/ BYURK, Icelandic: [pjœr̥k ˈkvʏðmʏntsˌtouhtɪr̥] ^ⓘ; born 21 November 1965), known mononymously as Björk, is an Icelandic singer, songwriter, composer, record producer, and actress. Noted for her distinct voice, three-octave vocal range, and eccentric public persona, she has developed an eclectic musical style over a career spanning four decades, drawing on electronica, pop, dance, trip hop, jazz, and avant-garde music. She is one of the most influential pioneers in electronic and experimental music.

Born and raised in Reykjavík, Björk began her music career at the age of 11 and gained international recognition as the lead singer of the alternative rock band the Sugarcubes by the age of 21. After the Sugarcubes disbanded in 1992, Björk gained prominence as a solo artist with her albums Debut (1993), Post (1995), and Homogenic (1997), which blended electronic and avant-garde music and achieved significant critical success. Her later albums saw further experimentation, including the glitch-influenced Vespertine (2001), a cappella album Medúlla (2004), pop-focused Volta (2007), and Biophilia (2011), an interactive album with an accompanying iPad app. Following the death of her longtime co-producer Mark Bell, she collaborated with Venezuelan artist Arca on her albums Vulnicura (2015) and Utopia (2017), while Fossora (2022) marked her first venture as a sole producer.

With sales of over 40 million records worldwide, Björk is one of the best-selling alternative artists of all time. Several of her albums have reached the top 20 on the US Billboard 200 chart. Thirty-one of her singles have reached the top 40 on pop charts around the world, with 22 top 40 hits in the UK, including the top-10 singles "It's Oh So Quiet", "Army of Me", and "Hyperballad" and the top-20 singles "Play Dead", "Big Time Sensuality", and "Violently Happy". Her accolades and awards include the Order of the Falcon, five BRIT Awards, and 16 Grammy nominations (including nine in the Best Alternative Music Album category, the most of any artist). In 2015, Time named her one of the 100 most influential people in the world. Rolling Stone named her the 64th-greatest singer and the 81st-greatest songwriter of all time in 2023.

Björk starred in the 2000 Lars von Trier film Dancer in the Dark, for which she won the Best Actress Award at the 2000 Cannes Film Festival, and was nominated for the Academy Award for Best Original Song for "I've Seen It All". Björk has also been an advocate for environmental causes in Iceland. A retrospective exhibition dedicated to Björk was held at New York's Museum of Modern Art in 2015.

Björk Guðmundsdóttir was born on 21 November 1965 in Reykjavík. She was raised by her mother, Hildur Rúna Hauksdóttir (7 October 1946 – 25 October 2018), an activist who protested against the development of Iceland's Kárahnjúkar Hydropower Plant, having divorced from Björk's father, Guðmundur Gunnarsson, an electrician and union leader, after Björk was born. She and her mother moved into a commune. Her stepfather is Sævar Árnason, a former guitarist in the band Pops.

At six, Björk enrolled at Reykjavík school Barnamúsíkskóli, where she studied classical piano and flute. She also went to school with the father of fellow Icelandic singer Laufey. After a school recital in which Björk sang Tina Charles's 1976 hit "I Love to Love", her teachers sent a recording of her singing the song to the RÚV radio station, which at that time was Iceland's only radio station. The recording was broadcast nationally and, after hearing it, a representative of the Fálkinn record label offered Björk a recording contract. Her debut record, Björk, considered juvenilia, was recorded when she was 11 years old and was released in Iceland in December 1977.

During her teens, after the diffusion of punk rock music in Iceland, Björk formed the all-girl punk band Spit and Snot. In 1980, she formed a jazz fusion group, Exodus, collaborated in another group, JAM80, and graduated from music school. In 1981, she and bassist Jakob Magnússon formed another group, Tappi Tíkarrass ("Cork the Bitch's Ass" in Icelandic), and released the EP Bitið fast í vitið ("Bite Hard Into the Mind" in Icelandic), in August 1982. Their album Miranda was released in December 1983. The group was featured in the documentary Rokk í Reykjavík, with Björk being featured on the cover of the VHS release. Around this time, Björk met guitarist Þór Eldon and surrealist group Medusa, which also included poet Sjón, with whom she started a lifelong collaboration and formed a group, Rokka Rokka Drum. She described her time as part of Medusa as "a gorgeous D.I.Y. organic university: extreme fertility!" Björk appeared as a featured artist on "Afi", a track from the Björgvin Gíslason 1983 record Örugglega.

Due to the imminent cancelling of radio show Áfangar, two radio personalities, Ásmundur Jónsson and Guðni Rúnar, requested musicians to play on a last live radio show. Björk joined with Einar Melax (from the group Fan Houtens Kókó), Einar Örn Benediktsson (from Purrkur Pillnikk), Guðlaugur Kristinn Óttarsson and Sigtryggur Baldursson (from Þeyr), and Birgir Mogensen (from Spilafífl) to perform in the concert. The group developed a gothic rock sound. During this experience, Björk began to develop her vocalisation – punctuated by howls and shrieks. The project performed as Gott kvöld during the concert. When they later decided to keep playing together as a group, they used the name Kukl ("Sorcery" in Icelandic). Björk's acquaintance gave the group their studio to record in and released their first single in 1983. Their first big performance at a festival in Iceland was headlined by English anarchist punk band Crass, whose record label, Crass Records offered the band a record deal. The Eye was released in 1984, followed by a two-month tour in Europe, which also included a performance at Roskilde Festival in Denmark. This made Kukl the first Icelandic band to play at the festival. During this period Björk published a hand-coloured book of poems. Um Úrnat frá Björk was distributed in 1984.