- Name: Agatha Mary Clarissa Miller
- Born: 15 September 1890, Torquay, Devon, England
- Died: 12 January 1976 (aged 85), Winterbrook House, Wallingford, Oxfordshire, England
- Resting place: Church of St Mary, Cholsey, Oxfordshire
- Pen name: Mary Westmacott
- Occupation: Novelist - short story writer - playwright - poet - memoirist
- Genre : Murder mystery - detective story- crime fiction - thriller
- Literary movement: Golden Age of Detective Fiction
- Notable works:
- Murder on the Orient ExpressThe Murder of Roger Ackroyd Death on the Nile
- The Murder at the Vicarage Partners in Crime
- The A.B.C. MurdersAnd Then There Were NoneThe Mousetrap
- Archibald Christie (m. 1914; div. 1928)
- Max Mallowan (m. 1930)
- Children: Rosalind Hicks
- Relatives: James Watts (nephew)