John Costello can refer to:

John Costello (MLB pitcher), MLB pitcher
John A. Costello, former Taoiseach of Ireland
John M. Costello (1903–1976), U.S. Representative from California
John Costello (Artist), Maui based Painter & Wood Carver
John Costello (Webmaster), webmaster of GBATemp, and programmer of Oxbrowse and DSHobro