Mary MacCarthy (1882–1953) was a British writer, known for her involvement in the "Bloomsbury Group".
Mary MacCarthy was the daughter of the teacher and man-of-letters Francis Warre Warre-Cornish. She was commonly called Molly.
In 1906 she married the literary critic Desmond MacCarthy, with whom she had one daughter, Rachel.
Though prevented by progressive hearing-loss from full participation in group conversation, she was active in the Bloomsbury group, as demonstrated by her formation of its Memoir group and Novel group, and by coining the term "Bloomsberries" to describe its members.
Her sister Cecilia married William Wordsworth Fisher later Admiral. Her daughter Rachel married the biographer David Cecil.