Reay Tannahill was born on December 9, 1929 in Glasgow, Scotland, where she brought up. Her forename was the maiden name of her mother, Olive Reay. She was educated at Shawlands Academy, and obtained an MA in History and a postgraduate certificate in Social Sciences at the University of Glasgow. In 1958, she married Michael Edwardes but the marriage ended in divorce in 1983, he died in 1990. Until her death on November 2, 2007, she lived in a smart terrace house in London near Tate Britain.
Before started to write, she worked as a probation officer, advertising copywriter, newspaper reporter, historical researcher and graphic designer. She published her first non-fiction book in 1964. The international success came with the novel Food in History, her publisher suggested a companion volume on the second great human imperative, Sex in History. For her 2002 revised edition of 'Food in History, she won the Premio Letterario Internazionale Chianti Ruffino Antico Fattore. She also wrote historical romance novels, and in 1990, her novel Passing Glory won in 1990 the Romantic Novel of the Year Award by the Romantic Novelists' Association. She belonged to the Arts Club and the Authors' Club, and was chairman of the latter from 1997 to 2000.