John Costello may refer to:
- John Costello (baseball) (born 1960), American baseball pitcher
- John A. Costello (1891–1976), Taoiseach of Ireland
- John M. Costello (1903–1976), U.S. Representative from California
- John Costello (Medal of Honor recipient) (1850–?), U.S. Navy sailor and Medal of Honor recipient
- John Edmund Costello (investigative author) (b. Newbury, 1943may3-1995aug26) who wrote on spies including Oleg Tsarev and Ursula Kuczynski, and was murdered suspiciously in 1995.