Alan Seymour, born 1927 in Fremantle, Western Australia, is an Australian playwright and author best known for his play The One Day of the Year (1958). When Alan was nine, his father was killed in a wharf accident, after that he was raised by his sister May and her husband. Educated at Perth Modern School, he left at the age of fifteen after failing to complete the Junior Certificate. He then worked as a radio announcer in commercial radio. During his time there he wrote a number of short radio plays which were broadcast live. In 1945 he moved to Sydney where he found employment as an advertising copy-writer.

After the war, he returned to Perth working as a freelance writer for ABC radio. Late 1949, Seymour returned to Sydney where he became an educational and freelance drama writer for ABC Radio and later television. From 1953 to 1957 he was a theatrical director for the Sydney Opera Group. His first play, Swamp Creatures, was a finalist in the London Observer play competition in 1957.

Seymour left Australia and worked in London as a television writer, producer and commissioning editor with the BBC and as a theatre critic for The London Magazine. From 1966–1971 he lived in Turkey and wrote novels, stage plays and magazine articles. From 1974–1981 Seymour was a script editor and occasional producer with BBC Television, after which he returned to freelance writing He returned to live in Sydney in 1995

His best-known play, The One Day of the Year was written in 1958 for an amateur play-writing competition, inspired by an article in the University of Sydney newspaper Honi Soit lambasting Anzac Day. Although Seymour is best known in Australia for The One Day of the Year, his international reputation relates not only to this early play, but also to his many screenplays, television scripts and adaptations of novels for film and television