Mary O'Sullivan

Mary O'Sullivan may refer to:
 * Mary Blanche O'Sullivan (1860–?), Canadian teacher, writer, and editor
 * Mary Josephine Donovan O'Sullivan (1887–1966), Irish professor of history
 * Mary Kenney O'Sullivan (1864–1943), American organizer in the early U.S. labor movement
 * Mary O'Sullivan (camogie), Irish camogie-player
 * Mary Rhys-Jones (née O'Sullivan) (born 1965), British charity worker and secretary, mother of Sophie, Countess of Wessex