The Cabinet has agreed to move the country to Level 5 restrictions from midnight until 31 January, at least.
Level 5 is the highest level under the Government's medium-term Covid plan.
In an address to the nation, Taoiseach Micheál Martin outlined what the new restrictions mean.
The reopening of schools after the Christmas break will be delayed until 11 January.
However, childcare facilities and crèches will remain open.
Outdoor playgrounds and play areas will remain open with protective measures.
People will only be able to exercise within five kilometres of their home.
People will be allowed to travel outside their five kilometres for work, education or other essential purposes.
People should work from home unless providing an essential service. A list of essential services can be found here.
All household visits are prohibited, including social visits to gardens, except for essential family reasons or those in your support bubble.
People will be permitted to meet up and exercise with residents from one other household in an outdoor setting.
All non-essential business, including gyms, will have to shut by the close of business tomorrow.
Essential retail outlets, such as supermarkets, fuel forecourts and pharmacies, can remain open.
Pubs, restaurants and cafes will only be allowed to operate a takeaway or delivery service.
The number of people who can attend a funeral during the period of Level 5 restrictions is 10.
The number of guests allowed to attend weddings is 25 until 2 January and will be reduced to six after from 3 January.
Religious services will be available online.
An eviction moratorium is to be reintroduced from midnight.
Hotels, guesthouses and Bed and Breakfasts can remain open, but only for guests who are providing an essential service.
Museums, galleries and other cultural attractions will remain closed, while libraries will be available for online services only.
No indoor or outdoor exercise group activities, including those involving children, should take place.
Construction sites will remain open, as will most manufacturing facilities.
Visits to long-term residential care facilities are suspended, except in compassionate circumstances.
Public transport will operate at 25% capacity to allow those providing essential services to get to work.