Nightclubs will have to close from December 7th to January 9th, while bars and restaurants must revert to rules in existence prior to October 22nd.
That means table service only ,1 metre between tables and a maximum of six adults per table.
However closing time will remain at midnight.
There will be a maximum of 50% capacity at entertainment, cultural, community and sporting events indoors, which must be fully seated.
Announcing the measures, Taoiseach Micheál Martin says if the spread of the omicron variant takes hold, there is the potential for a serious crisis.
Other measures announced this evening, include gatherings in homes will be restricted to four households.
A Covid Pass will be required for gyms and leisure centres as well as hotel bars and restaurants.
