Gillian Catherine Gill (née Scobie, born June 12, 1942) is a Welsh-American writer and academic who specializes in biography. She is the author of Agatha Christie (1990), Mary Baker Eddy (1998), Nightingales: The Extraordinary Upbringing and Curious Life of Miss Florence Nightingale (2004), and We Two: Victoria and Albert, Rulers, Partners, Rivals (2009).
Born in Cardiff, Wales, Gill attended Cardiff High School for Girls and graduated from the University of Cambridge with a first-class honours degree in French, Italian, and Latin. In March 1972 she obtained her Ph.D., also from Cambridge, for a thesis entitled André Malraux: A Study of a Novelist. After marrying, she emigrated to the United States and taught at Northeastern University, Wellesley, Harvard, and Yale, where she was a fellow of Jonathan Edwards College and director of the Women's Studies Program.