William John Banville (born 8 December 1945) is an Irish novelist, short story writer, adapter of dramas, and screenwriter. He also had a 30-year career working in the Irish newspaper industry and served as literary editor of The Irish Times from 1988 until 1999.

Born and raised in Wexford town in the southeast of Ireland, he published his first book, a collection of short stories titled Long Lankin, in 1970. His first novel, Nightspawn, appeared in 1971, followed by his second, Birchwood, two years later. His "Revolutions Trilogy", published between 1976 and 1982, comprises works named after renowned scientists: Doctor Copernicus, Kepler and The Newton Letter. His next work, Mefisto, had a mathematical theme, and, in combination with the three books from the "Revolutions Trilogy," is the fourth book from the "Scientific Tetralogy." His 1989 novel The Book of Evidence began the "Frames Trilogy," dealing with the work of art; it was completed by Ghosts and Athena. His thirteenth novel, The Sea, won the Booker Prize in 2005. In addition, he publishes crime novels as Benjamin Black, most of which feature the character of Quirke, an Irish pathologist based in 1950s Dublin. His alternative history novel The Secret Guests (2020) was published under the name B. W. Black.

Banville has won the 1976 James Tait Black Memorial Prize, the 2003 International Nonino Prize, the 2005 Booker Prize, the 2011 Franz Kafka Prize, the 2013 Austrian State Prize for European Literature and the 2014 Prince of Asturias Award for Literature. He was elected a Fellow of the Royal Society of Literature in 2007. Italy made him a Cavaliere of the Ordine della Stella d'Italia (a knighthood) in 2017. He is a former member of Aosdána, having voluntarily relinquished the financial stipend in 2001 to another, more impoverished, writer. He is considered a contender for the Nobel Prize in Literature. He lives in Howth, Dublin.

William John Banville was born to Agnes (née Doran) and Martin Banville, a garage clerk, in Wexford, Ireland. He is the youngest of three siblings; his older brother Vincent is also a novelist and has written under the name Vincent Lawrence as well as his own. His sister Anne Veronica "Vonnie" Banville-Evans has written both a children's novel and a memoir of growing up in Wexford. Banville stole a collection of Dylan Thomas's poetry from Wexford County Library while in his teens.

Banville was educated at CBS Primary, Wexford, a Christian Brothers school, and at St Peter's College, Wexford. Despite having intended to be a painter and an architect, he did not attend university. Banville has described this as "A great mistake. I should have gone. I regret not taking that four years of getting drunk and falling in love. But I wanted to get away from my family. I wanted to be free." In contrast, he has stated that college would have had little benefit for him: "I don't think I would have learned much more, and I don't think I would have had the nerve to tackle some of the things I tackled as a young writer if I had been to university—I would have been beaten into submission by my lecturers."

After school, Banville worked as a clerk at Aer Lingus, which allowed him to travel at deeply discounted rates. He took advantage of these rates to travel to Greece and Italy. He began working as a sub-editor at The Irish Press in 1969 and subsequently worked as a sub-editor at The Irish Times. He was appointed literary editor of The Irish Times in 1988, a position he held until 1999.

In 1969, Banville married the American textile artist Janet Dunham, whom he met in San Francisco the previous year while she was a student at the University of California, Berkeley. The couple had two sons together. Their marriage broke down after Banville had an affair with a neighbour, Patricia Quinn, who subsequently became director of the Arts Council of Ireland. Banville had two daughters with Quinn, born around 1990 and 1997. Despite separating, Banville and Dunham never divorced and he described them as remaining "on good terms." Dunham died at Blackrock Clinic on 22 November 2021, after which Banville stated that he experienced "brain fog" due to grief and was unable to write for six months. In a 2024 interview, he expressed regret over his relationship history, saying: "I caused Janet such anguish. I have caused Patricia Quinn such anguish. I wasn’t good with my children. I was not a good parent. I am not a good person. I am selfish. But I have to have responsibility.”

Banville published his first book, a collection of short stories titled Long Lankin, in 1970. He has disowned his first published novel, Nightspawn, describing it as "crotchety, posturing, absurdly pretentious".