Costigan (Irish: Mac Oistigin) is an Irish surname and may refer to:
- Daniel Costigan, former Commissioner of An Garda Síochána
- Edward P. Costigan (1874–1939), US senator from Colorado
- Francis Costigan, early Indiana architect
- Frank Costigan, (1931–2009) Australian QC and commissioner in the Royal Commission on the activities of the Federated Ship Painters and Dockers Union (known as the Costigan Commission)
- Giovanni Costigan (1905–1985), historian
- George Costigan (born 1947), a British television actor
- Howard Costigan (1904-1985), American political functionary
- Neville Costigan, Australian rugby league footballer
- James Costigan, screenwriter
- Peter Costigan, (1935–2002), Australian journalist, former Lord Mayor of Melbourne
- Billy Costigan, a character in the Martin Scorsese film, The Departed, played by Leonardo DiCaprio
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