The project welcomes all who wish to work together to discover our common Sweeney (Mac Suibhne) heritage through sharing information and DNA testing results. Only through such cooperation can we succeed. All variant spellings are welcome. If your spelling variation is missing we will be glad to add it. The “Leabhar Chlainne Suibhne” chronicles the beginning of the Sweeney surname. The first “Suibhne" is told to have been a descendant of an Irish prince of the O’Neill dynasty who arrived in Argyll, Scotland in the 11th century. Generations later the Mac Suibhne arrive in (or return to) northern Ireland as Gallowglass, elite mercenary warriors. They establish themselves in County Donegal at Fanad and Doe and later near Dunkineely. At their height these three branches, Mac Suibhne Fánad, Mac Suibhne na d’Tuath, and Mac Suibhne Boghaineach controlled large territories. But by the middle of the 17th century their power is gone and their castles and lands are controlled by the English. In following centuries waves of Irish migrated across the globe. They were fleeing oppression, hunger, or just seeking a better opportunity. Can our DNA confirm or refute that we are a branch of the O’Neills? Can our DNA show us traces of the Fanad, Doe, and Banagh branches? Can our DNA help us figure out when and where our ancestors first arrived overseas? Given enough men with Autosomal and deep y-DNA testing we might answer these questions.