Under new Irish Government rules, all passengers arriving into the State from designated “category 2” countries after 4am on the morning of Friday, March 26 are required to pre-book accommodation in a mandatory quarantine hotel.
There is a list of these "category 2" countries here. Under the new rules, any passenger that arrives into the State without the required negative or not detected COVID-19 PCR test will also be subject to mandatory quarantine.
Before travelling to Ireland, you must reserve and pay for a place in a mandatory quarantine hotel.
If you arrive in Ireland from a location that is not a “category 2” State, and you have the required evidence of a negative/not detected COVID-19 PCR test, under Irish Government rules you must quarantine at home.
There is more information on the Irish Government’s website and on the Government’s quarantine hotel booking system.