The O'Neill dynasty was a prominent Irish royal family that ruled over the province of Ulster in Ireland. They were known for their leadership and military prowess, particularly during the late medieval and early modern periods. The dynasty's most famous figure is Hugh O'Neill, who led a significant rebellion against English rule in the late 16th century, known as the Nine Years' War. The O'Neills played a crucial role in the history of Ireland, especially in the context of the struggle for independence from English control. Their influence waned after the defeat in the Nine Years' War, leading to the eventual decline of their power and the establishment of English dominance in Ireland.