Mary Day

Mary Day may refer to:

• Mary Day (dance teacher) (1910–2006), founder of The Washington Ballet
• Mary Anna Day (1852–1924), American botanist and librarian
• Mary E. Day, in the 2005 Supreme Court opinion Varian v. Delfino
• Mary L. Day (1836–?), American memoirist
• Mary Gage Day (1857–1935), American physician and medical writer
• Mary Louise Day (1968–2017), teenage girl who mysteriously disappeared from her home

• Marian feast days