Mary Simpson may refer to:

• Mary Simpson (priest) (1925–2011), one of the first women to be ordained an Episcopal priest (1977)
• Mary Simpson (Northern Ireland politician), unionist politician in Northern Ireland in the 1970s and 1980s
• Mary Simpson (violinist), violinist known for performing in Yanni's orchestra
• Mary Elizabeth Simpson (1865–1948), New Zealand religious teacher, healer and writer
• Mary Ellen Simpson, musician in The Ace of Cups
• Mary Kell Simpson (1903–1970), South Australian physiotherapist later known as Dorothy Kell Finnis
• Mary Simpson (house servant)
• Mary Jean Simpson, American scholar and public servant
• Mollie Evans (1922-2016), British antique dealer, born Mary Simpson

• Mary Simpson, fictional character in the 1632 book series
• Mary Simpson, fictional character on the TV series The Andy Griffith Show
• Mary Simpson, fictional character in the film Two Mafiamen in the Far West