Nora Barnacle Joyce (born Norah Barnacle; 21 March 1884 – 10 April 1951) was the muse and wife of Irish author James Joyce.

Barnacle and Joyce's life together has been the subject of much popular interest. Nora Barnacle, a 1980 play by Maureen Charlton, was made about their relationship. Barnacle was the subject of a 1988 biography, Nora: A Biography of Nora Joyce, by Brenda Maddox, which was adapted into a 2000 Irish film, Nora, directed by Pat Murphy, and starring Susan Lynch and Ewan McGregor.

Barnacle was born in a Galway workhouse on 21 March 1884. Her entry in the birth register, which gives her first name as "Norah" (the spelling she used until she met Joyce), is dated 22 March. Her father, Thomas Barnacle, a baker in Connemara, was an illiterate man who was 38 years old when she was born. Her mother, Annie Honoria Healy, was 28 and worked as a dressmaker. The unusual surname Barnacle is derived from the Irish Ó Cadhain, usually anglicised as Coyne, Kyne, or Cohen or Coen, but in Irish, cadhan means "wild goose", and some families made the translation to Barnacle, after the barnacle goose.

From 1886 to 1889, Barnacle's parents sent her to live with her maternal grandmother Catherine Mortimer Healy. During these years, she began studies at a convent, eventually graduating from a national school in 1891. In 1896, 12-year-old Barnacle completed her schooling and began to work as a porteress and laundress. In the same year, her mother threw her father out for drinking and the couple separated. Barnacle went to live with her mother and her uncle, Tom Healy, at 4 Bowling Green, Galway. This house has since been converted into a small museum dedicated to Nora.

In 1896, at age 12, Barnacle fell in love with a teenager named Michael Feeney, who died soon after of typhoid and pneumonia. In a dramatic coincidence, another boy she loved, Michael Bodkin, died in 1900 – causing some of her friends to call her "man-killer". Joyce later referenced these incidents in the final short story in Dubliners, "The Dead". It was rumoured that she sought comfort from her friend, budding English theatre starlet Laura London, who introduced her to a Protestant named Willie Mulvagh. In 1903, she left Galway after her uncle learned of the affair and friendship, and went to Dublin where she worked as a chambermaid at Finn's Hotel (later the name of the hotel was used as the title for a posthumously published collection of ten short narrative pieces written by Joyce, Finn's Hotel, in 2013).

Barnacle met Joyce on 10 June 1904 while in Dublin and they had their first romantic liaison on 16 June. Joyce later chose 16 June 1904 as the date for the setting for his novel Ulysses and the date has come to be known and celebrated around the world as Bloomsday. The 1904 rendezvous began a long relationship that eventually led to marriage in 1931 and continued until Joyce's death.

Barnacle's and Joyce's relationship was complex. They had different personalities, tastes and cultural interests. Of their first meeting, she recalled: "I mistook him for a Swedish sailor – His electric blue eyes, yachting cap and plimsolls. But when he spoke, well then, I knew him at once for just another Dublin jackeen chatting up a country girl." The numerous erotic letters they exchanged suggest they loved each other passionately. These are also of interest because of Joyce's lifelong dislike of swearing and crude language. Joyce seems to have admired and trusted her, and Barnacle clearly loved Joyce and trusted him enough to agree to leave Ireland with him for the Continent. In anticipation of the move to Paris, she began studying French.

In 1904, Barnacle and Joyce left Ireland for continental Europe and the following year set up house in Trieste (at that time in Austria-Hungary). On 27 June 1905, Nora Barnacle gave birth to a son, Giorgio and later to a daughter, Lucia, on 26 July 1907. A miscarriage in 1908 coincided with the beginning of a difficult time for both. Though she remained by his side, and the couple were legally married in London in 1931, she complained to her sister both about his personal qualities and his writings. In these letters to her sister, she said he drank too much and wasted too much money. As for his literary activity, she lamented that his writings were obscure and lacking in sense. She was always fiercely proud of him, although she occasionally expressed impatience at his meetings with other artists and admitted she would have preferred him to have been a musician—in his youth, he was a talented singer—rather than a writer.