Medúlla is the fifth studio album by Icelandic recording artist Björk. It was released on 30 August 2004 in the United Kingdom by One Little Indian Records and in the United States by Elektra Entertainment. After the release of her electronic-influenced previous album Vespertine (2001), Björk intended to make an album almost entirely a cappella constructed with human vocals, in opposition to the previous album's intense process of composition and multiple layers of instrumentation. The album's title derives from the Latin word for "marrow".

Medúlla received critical acclaim from music critics, with many calling it "unique", although others deemed it "confusing". The album was also commercially successful, reaching number one in Belgium's Wallonia, France and Iceland, whilst also peaking within the top ten in the United Kingdom. Medúlla is estimated to have sold more than a million copies worldwide, and received two nominations at the 47th Grammy Awards.

Two singles were released from Medúlla: "Who Is It" and "Triumph of a Heart", with both charting inside the top 40 in the United Kingdom and the top 10 in Spain. Björk further promoted the album by performing the song "Oceania" at the 2004 Summer Olympics opening ceremony, Friday Night with Jonathan Ross and other television and radio shows. Other than these few performances, no concerts or tours were arranged to promote Medúlla, as Björk thought it would be too difficult to play the songs live. In 2015, the album was adapted into an opera at the Brussels opera house La Monnaie by Sjaron Minailo and Anat Spiegel.