The Irish Dark Age refers to a period of apparent economic and cultural stagnation in late pre-historic Ireland, lasting from c. 100 BC to c. 300 AD.
The phrase was coined by Thomas Charles-Edwards to describe a gap in the archaeological record coinciding with the Roman Empire in Britain and continental Europe. Charles-Edwards notes the lack of continuity between Ptolemy's writings on the peoples of second-century Ireland and writings in ogham in the fifth century. Pollen data extracted from Irish bogs indicates a decrease in human impact on plant life in the bogs in the third century. Charles-Edwards has suggested that the decrease in agricultural productivity might be due to a large-scale export of slaves to Roman Britain.
Others such as Joseph Raftery, Barry Raftery, and Donnchadh Ó Corráin have drawn attention to a decline in human settlement and activity in Ireland, starting from around the first century BC.