John Aidan Costello (Gaelic: Eoin Aodhan MacCostello) (September 10, 1901 - May 9, 1994) was an Irish politician and soldier best known for serving as the commander of the Irish forces in England during the Irish intervention in the English Anarchy, a military campaign he later became a fierce critic of. Costello became a moderate, secular Conservative politician in the Dail Eireann after retiring from the army in 1964 and was a two-time Presidential candidate, running in 1967 and 1971. Costello is credited for helping repair the Irish right and install a new intellectual renaissance for the Conservative Party, which came to represent the Irish center-right as the opposition party after the decline of the Christian Democrats. He declined to run in the 1976 general election to contest the Presidency and retired from politics shortly thereafter having spent over a decade in the Dail. Costello was extremely supportive of the Constitutional reforms of 1982, helping give President Lynch the support from the right that he needed.