Mary O'Leary
Mary O'Leary may refer to:

 Mary O'Leary (producer), American soap opera producer
 Mary O'Leary (camogie), Irish former camogie player
 Mary O'Leary (Big Brother), Irish reality show contestant
 Liz Truss (born 1975), British former Prime Minister, whose birth name was Mary and is married to Hugh O'Leary