From 16 January 2021, all passengers arriving into Ireland will require a negative PCR COVID-19 Test taken within 72 hours prior to arrival.
Arrivals from Great Britain and South Africa will continue to require a negative/not detected PCR test and must continue to isolate for 14 days, even if they take a second test after arrival. Arrivals from red and grey list countries can shorten the isolation period on receipt of a negative/not detected result of a second PCR test taken no less than 5 days after arrival.
More information: https://bit.ly/3qhAUNy.