Thousands of homes will be built in Clonburris, a new south Dublin town.
An Bord Pleanala has approved plans for 8,400 homes.
The area runs from north of Clondalkin to Adamstown.
Three primary and three secondary schools will be built in phases, along with houses and apartments.
Mayor of South Dublin County Council Mark Ward says the homes are badly needed.
He said: 'We're in the midst of the biggest housing crisis in the history of the State. We had over 40 hours of meetings up in South Dublin County Council.
'We went through the plans bit by bit.
'2,700 of these houses will be public homes for people on the social housing list and for affordable housing too.
'People are feeling it a lot. If you're paying €2000 per month, you'll never be in a postition to save for a mortgage. We need to bring the rents down.
'As a result, we need to see home and communities built.'