The name can be traced back to Labradh Longseach, who was ruler of Ireland for eighteen years from 541 B.C. Longseach means mariner. There are two quite separate Lynch septs, or clans. In addition to the ancient Irish sept, there's a Norman one, too. The de Lenchs came to Ireland with the Anglo-Norman invasion; it is thought that this branch of the family is descended from the great emperor Charlemagne, who conquered most of western Christendom in A.D. 800. The family had connections with Linz in Austria and migrated westwards.

While the Lynchs are common in counties Antrim, Down, Cavan, Clare, Cork, and Tipperary, they are particularly connected with Co. Galway, where they were one of the famous Tribes of Galway. In the centre of Galway city stands Lynch's Castle, a fine mansion dating back to 1320. Once the residence of the Lynch family, it is now a bank branch. The history of the family is well detailed inside the building.