An Bord Pleanála has refused planning permission for more than 500 homes in north Dublin.
The project, which was initially given the go-ahead earlier this year, would have seen 432 apartments and 104 houses built on lands at St Paul's College in Raheny.
Locals were concerned that the development would destroy the nearby park of St Anne's.
Fine Gael Senator Catherine Noone has welcomed the news.
"Obviously we are in the middle of a housing crisis, we all accept the difficulties there," she said.
"But this is a beautiful park that is used by so many residents in the area. If we are going to be building, we should be building on old industrial sites, brownfield sites.
"There's plenty of land available in the country without building on the likes of a beautiful resource for the people of north Dublin like St Anne's Park."