Costigan (Irish: Mac Oistigin) is an Irish surname with higher concentrations in Counties Laois, Tipperary and Kilkenny. Costigan is thought to be a branch of the Mac Giolla Phádraig dynasty of Osraige. Notable people with the surname include:
Christopher Costigan, explorer of the Jordan River and Dead Sea in 1835
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
James Costigan, screenwriter
Jason Costigan, Australian Liberal National politician and former rugby commentator
John Edward Costigan, American artist
John Costigan (hurler)
Keith Costigan, former soccer player, and television sports analyst
Michael Costigan (entrepreneur)
Michael Costigan (film producer)
Michael Costigan (youth speaker)
Neville Costigan, Australian rugby league footballer
Peter Costigan, (1935–2002), Australian journalist, former Lord Mayor of Melbourne
Sandra Costigan, former field hockey player
Fictional characters:
Billy Costigan, a character in the Martin Scorsese film, The Departed, played by Leonardo DiCaprio
Captain Costigan, a character in the novel Pendennis, by William Makepeace Thackeray.
Sailor Steve Costigan, a character created by Robert E. Howard
Conway Costigan, a character in E.E. Smith's Triplanetary
Jerry, Grace and Russell Costigan, characters in Robert B. Parker's novel "A Catskill Eagle"
