Developers have lodged plans for nearly 3,600 homes in four sites in Dublin and Cork.
In Dublin, there are proposals for 995 apartments in Swords and 730 apartments in Ashtown.
In Cork, there are plans for 1,100 apartments in Centre Park Road and 753 homes in Ballyvolane.
Cork city councilor Kenneth O'Flynn said the developments would help address the housing crisis.
"There's an absolute need for this type of development. Cork is to be taken seriously as a counterbalance city for Dublin.
"Of course there are structural issues that have to be addressed as well with these large developments but they are most welcome and there is a serious need for private and public housing in Cork at the moment.
"The rental market is extremely expensive down here in Cork."