First Minister Mark Drakeford said a short, sharp, shock to turn back the clock, slow down the virus, and give us more time” was agreed after discussions with the Welsh cabinet.
The firebreak, which starts on Friday, will cover the half-term holiday and run until November 9.
Mr Drakeford has said that the move was necessary due to the increasing number of hospitalisations in the last few weeks.
He said that if it worsens “even more extreme measures” will be put in place.
What are the rules of the lockdown in Wales, and can Brits visit Wales from the rest of the UK?