Mary Sinclair (disambiguation)

Mary Sinclair (1922–2000) was an American actress

Mary Sinclair may refer to:

• Mary P. Sinclair (1918–2011), American environmental activist
• Mary Craig Sinclair (1882–1961), writer and the wife of Upton Sinclair
• Mary Emily Sinclair (1878–1955), American mathematician
• May Sinclair, pseudonym of Mary Amelia St. Clair (1863–1946), a popular British writer