Hospitality venues, cinemas and theatres will have to close at 8pm each night, from tonight.
It's part of efforts to contain the spread of the highly-transmissible new Omicron variant.
The restrictions will be in place until the end of January, but are being kept under review.
New financial measures aimed at supporting affected businesses are expected to be announced by government shortly.
Meanwhile, the Chief Medical Officer's urging anyone eligible for a booster to avail of it as soon as possible.
It has taken less than two weeks for Omicron to become the dominant strain of Covd-19 in Ireland.
The variant now accounts for 52 per cent of cases - it comes as 5,124 new coronavirus infections have been confirmed.