The Farrell or O'Farrell clan (Ó Fearghail in Irish) is an Irish clan that traces its origins back to the battle of Clontarf in 1014. The escendants of Fearghal, who fought alongside Brian Boru at the battle of Clontarf, took the surname of Uí Fhearghail (descendants of Fearghal). The Uí Fhearghail went on to become Princes of the territory of Anghaile (Annaly), roughly corresponding to present day County Longford, their chieftain sitting at Longphort Uí Fhearghail (O'Farrell's stronghold), present day Longford town. Another site associated with the clan was Moatfarrell (Móta Uí Fhearghail), in the east of Annaly between the present day towns of Ballinalee and Edgeworthstown.