Lucia Anna Joyce (26 July 1907 – 12 December 1982) was an Irish professional dancer and the daughter of Irish writer James Joyce and Nora Barnacle. Once treated by Swiss psychiatrist Carl Jung, Joyce was diagnosed as schizophrenic in the mid-1930s and institutionalized at the Burghölzli psychiatric clinic in Zurich. In 1951, she was transferred to St Andrew's Hospital in Northampton, where she remained until her death in 1982. She was the aunt of Stephen James Joyce, who was the last descendant of James Joyce.

Lucia Anna Joyce was born in the Ospedale Civico di Trieste on 26 July 1907. She was the second child of Irish writer James Joyce and his partner (later wife) Nora Barnacle, after her brother Giorgio. As her parents were expatriates living in Trieste, Lucia's first language was Italian. In her younger years, she trained as a dancer at the Dalcroze Institute in Paris. She studied dancing from 1925 to 1929, training first with Jacques Dalcroze, followed by Margaret Morris, and later with Raymond Duncan (brother of Isadora Duncan) at his school near Salzburg. In 1927, Joyce danced a short duet as a toy soldier in Jean Renoir’s film adaptation of Hans Christian Andersen's "La Petite marchande d’allumettes" (The Little Match Girl). She furthered her studies under Lois Hutton, Hélène Vanel, and Jean Borlin, lead dancer of the Ballet suédois.

In 1928, she joined "Les Six de rythme et couleur," a commune of six female dancers that were soon performing at venues in France, Austria, and Germany. After a performance in La Princesse Primitive at the Vieux-Colombier theatre, the Paris Times wrote of her: "Lucia Joyce is her father's daughter. She has James Joyce's enthusiasm, energy, and a not-yet-determined amount of his genius. When she reaches her full capacity for rhythmic dancing, James Joyce may yet be known as his daughter's father."

On 28 May 1929, she was chosen as one of six finalists in the first international festival of dance in Paris held at the Bal Bullier. Although she did not win, the audience, which included her father and the young Samuel Beckett, championed her performance as outstanding and loudly protested the jury's verdict. It has been alleged that when Lucia was 21, she and Beckett (who was her father's secretary for a short time) became lovers. Their relationship lasted only a short while and ended after Beckett, who was involved with another woman at the time, admitted that his interest was actually in a professional relationship with James Joyce, not a personal one with Joyce's daughter.

At the age of 22, Joyce, after years of rigorous dedication and long hours of practice, decided "she was not physically strong enough to be a dancer of any kind". Announcing she would become a teacher, she then "turned down an offer to join a group in Darmstadt and effectively gave up dancing."

Her biographer Carol Shloss, however, argues that it was her father who finally put an end to her dancing career. James reasoned that the intense physical training for ballet caused her undue stress, which in turn exacerbated the long-standing animosity between her and her mother Nora. The resulting incessant domestic squabbles prevented work on Finnegans Wake. James convinced her she should turn to drawing lettrines to illustrate his prose and forgo her deep-seated artistic inclinations. To his patron Harriet Shaw Weaver, James Joyce wrote that this resulted in "a month of tears as she thinks she has thrown away three or four years of hard work and is sacrificing a talent".

Lucia Joyce started to show signs of mental illness in 1930, including a time period during which she was involved with Samuel Beckett, then a junior lecturer in English at the École normale supérieure in Paris. In May 1930, while her parents were in Zurich, she invited Beckett to dinner, hoping "to press him into some kind of declaration." He flatly rejected her, explaining that he was only interested in her father and his writing.

By 1934, she had participated in several affairs, with her drawing teacher Alexander Calder, another expatriate artist Albert Hubbell, and Myrsine Moschos, assistant to Sylvia Beach of Shakespeare and Company. As the year wore on, her condition had deteriorated to the point that James had Carl Jung take her in as a patient. Soon after, she was diagnosed with schizophrenia at the Burghölzli psychiatric clinic in Zurich. In 1936, James consented to have his daughter undergo blood tests at St Andrew's Hospital in Northampton. After a short stay, Lucia Joyce insisted she return to Paris, the doctors explaining to her father that she could not be prevented from doing so unless he had her committed. James told his closest friends that "he would never agree to his daughter being incarcerated among the English."