Margaret Barnes may refer to:
Margaret Ayer Barnes (1886–1967), American playwright, novelist and short-story writer Margaret Anne Barnes (1927–2007), American writer Margaret Barnes (marine biologist) (1919–2009), British marine biologist Margaret Barnes of Westminster (16th-century), English tavern keeper, known as Long Meg of Westminster Margaret Barnes (javelin thrower) (born 1920), American javelin thrower, runner-up at the 1938 USA Outdoor Track and Field Championships