The new measures, while will apply to arrivals from England, Wales and Scotland, will come into effect on Saturday (9 January).
They will also apply to those whose journey originated in South Africa.
Arrivals will also be advised to self-isolate for 14 days upon their arrival in Ireland.
In a statement, Ireland’s Department for Foreign Affairs said: "From 9 January onwards, any passengers arriving into Ireland whose journey originated in Great Britain or South Africa are required to have a negative / not detected result from a pre-departure Covid-19 PCR test taken within 72 hours before their arrival in Ireland.
