The Ancient Order of Hibernians (AOH; Irish: Ord Ársa na nÉireannach[1][2]) is an Irish Catholic fraternal organization.

Members must be Catholic and either born in Ireland or of Irish descent.

Its largest membership is now in the United States, where it had been founded in New York City in 1836.

Its name is adopted by groups of Irish immigrants in the United States, its purpose to act as guards to protect Catholic churches from anti-Catholic forces in the mid-19th century, and to assist Irish Catholic immigrants, especially those who face discrimination or harsh coal mining working conditions.

Many members in the coal mining area of Pennsylvania have a background with the Molly Maguires.

It becomes an important focus of Irish American political activity.