This chapter begins by surveying the linguistic history of Ireland. Although it is situated on the periphery of the British Isles, there is evidence of contact between the island, other regions of Britain and indeed other countries in western Europe for centuries. It explores early and later contacts between the indigenised Celts and more recent colonisers and immigrants, including the Normans, the English, the Scots and twentieth-century settlers from the European Union prior to Brexit. These contacts have created a set of contemporary Irish English varieties that are not only distinctive with respect to other world Englishes but are also differentiated diatopically, ethnically and socially. Two main topics are addressed. The degree to which Irish English from different time frames is structurally similar to other dialects spoken elsewhere is considered alongside evaluating the extent to which contemporary Irish Englishes vary internally and externally with respect to their lexis, phonology, morphosyntax and discourse pragmatics. Some space is also devoted to examining how the study of Irish English has developed and what directions research might take in the twenty-first century in response to new approaches to modelling linguistic contact as well as the availability of larger and more diverse digital datasets.