In Irish mythology the Fir Bolg (Fir Bholg, Firbolg) were one of the races that inhabited the island of Ireland prior to the arrival of the Tuatha De Danann. In far antiquity the Fir Bolg were the rulers of Ireland (at the time called Eriu) immediately before the arrival of the Tuatha De Danann, or the Children of Danu, whom many interpret as the Gaelic gods. The King of the Tuatha De Danann, Nuada, sued for half the island for his people, but the Fir Bolg king refused. They met at the Pass of Balgatan, and the ensuing battle - the Battle of Mag Tuired - went on for four days. During the battle, Sreng, the champion of the Fir Bolg, challenged Nuada to single combat. With one sweep of his sword, Sreng cut off Nuada's right hand. However, the Fir Bolg were defeated and their king, Eochaidh, was slain by a goddess, The Morrigan, though the fierce efforts of their champion Sreng saved them from utter loss.
Contributions by Nicknack009, Felix Folio Secundus, and SmackBot.