Cabinet Ministers have approved an extension of the lockdown until March 5th, along with new rules around travel.
Taoiseach Micheál Martin has said the number of people in hospital and ICU beds is still to high to consider lifting restrictions.
People are being urged to stay at home for the next six weeks except for essential reasons.
People breaching the 5km travel limit will be subject to increased fines.
Work is continuing on school reopening plans, with Tánaiste Leo Varadkar suggesting there'll be a "phased re-opening of schools across February and March" starting with special needs education.
A range of international travel restrictions have also been confirmed, with mandatory quarantine required for anyone arriving into Ireland without a negative PCR test.
Mandatory quarantine for those who arrive here without a PCR test
Mandatory quarantine for people arriving from Brazil & South Africa
End of visa-free travel from those places until March 5th
— Seán Defoe (@SeanDefoe) January 26, 2021
Anyone arriving here without a test will also be subject to a fine of €2,500 and/or six months in prison.
Mandatory quarantine will also apply for anyone coming from South Africa and Brazil, and visa-free travel from those countries has been suspended until at least early March.
All other passengers will be legally required to quarantine at home - a measure which previously hasn't been enforced.
The legal requirement will also apply to anyone who arrives in the Republic via Northern Ireland.
Legislative work is now underway to introduce the necessary laws so the rules can apply to Irish and EU citizens, and the Tánaiste said it will take a number of weeks for those laws to come into force.
The rules for people from other areas will be able to come into effect shortly.
More gardaí will also be deployed at ports and airports to clamp down on non-essential travel.
'Stay at home'
Taoiseach Micheál Martin said: “The current level five restrictions are having a very positive effect on the profile of the disease in the country.
“The sacrifices people are making in their homes, families, businesses and communities are bringing us in the right direction.”
However, he said current progress is not enough to relieve the pressure on the health service - and the goal now is to 'crush' the level of the virus in the community.
He said people should stay at home for the next six weeks unless absolutely essential.
The Taoiseach said: “The road we are on is hard. The length of time we have had to live with restrictions and the proximity of vaccination makes it even harder… but it is the road we must take together.
"We have done it before, and we can do it again.”