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