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 per cent 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.
He's called on people to pull together to face the challenge ahead: