Ó Fearghail is a family name of the Irish nobility from County Longford who were historically the Princes of Annaly.

The lineage of Fearghail produced chiefs of the Dál Messin Corb and the Uí Garrchon.

[2] By 1618, the Ó Fearghail of Longford were finally deposed as Princes of Annaly by King James I, losing all of their lands and privileges.

After the fall of the tribal Gaelic Order, many became tenants of their old land with English and Scottish landlords.

A number of O'Farrell men served in an Irish regiment of the Spanish Army in the Eighty Years' War.