Mesolithic hunter-gatherers were the first Irish people known to modern science, leaving traces of their stone tools, middens and base camps throughout the country and following the coastline and river and lake systems in search of food.

While it is likely that there was a human presence in Ireland at some point during the Palaeolithic, the earliest confirmed groups of human settlers were small bands of hunter gatherers during the Mesolithic or Middle Stone Age. The land bridges which had previously connected Ireland to the continent had been submerged by this time so it is likely that the newcomers arrived from western Britain and/or Northern France in logboats or rafts. The hunter-gatherer life-cycles involved following migrating animals, fish and fowl along the river valleys and coastlines, reusing known base camps on a seasonal basis. These nomadic people have left little behind except discarded artefacts and midden sites (ancient dumps) found around the Irish Coast. The earliest known base-camp site is from Mount Sandel, Co Derry/Londonderry. Mesolithic burials are extremely rare in Ireland although an important site has recently been discovered at Hermitage on the Shannon where cremated cremated burials were deposited along with polished stone axes beneath large wooden posts. Ireland appears to have been relatively isolated in the later Mesolithic (c.5,500BC), using a distinct broad-blade technology different from that found in Britain and on the continent and in recent years an array of late-Mesolithic material has been identified in Western Connacht including several finds from the bed of the river Corrib in Galway city which may indicate the presence of a Late-Mesolithic base camp. A large series of dugout canoes which have been identified on the bed of the Corrib may also support this suggestion although vessels of this type remained in use throughout Irish prehistory.