The collection can be viewed in the reading room, and an increasing selection are available online.
While most of the collections are historical there are also some contemporary collections.
Subject matter ranges from topographical views to studio portraits and from political events to early tourist photographs.
The NPA's new exhibition Power and Privilege: Photographs of the Big House in Ireland 1858-1922 opens on 12 August and will run until December 2010.
This selection from the National Library of Ireland's photographic collections captures aspects of the Big House throughout the island of Ireland from 1858-1922. The Big House was a microcosm of power and privilege in the Irish countryside. These photographs record a moment in the life of a range of Irish Big Houses during a period of radical change. Visitors to the exhibition can enjoy uncovering new information on the Big House in Ireland 1858-1922, such as on family history, garden design, transport, and recreational activities