The O'Donnell dynasty were the dominant Irish clan of the kingdom of Tyrconnell in Ulster in the north of medieval and early modern Ireland.

Tyrconnell, also spelled Tirconnell and Tirconaill, was a kingdom of Gaelic Ireland. It is associated geographically with present-day County Donegal, which was officially named County Tirconaill between 1922 and 1927. At times it also included parts of County Fermanagh, County Sligo, County Leitrim, County Tyrone and County Londonderry at its greatest extent. The kingdom represented the core homeland of the Cenél Conaill people of the Northern Uí Néill and although they ruled, there were smaller groups of other Gaels in the area.