St. Brendan's Hospital was a psychiatric facility located in the north Dublin suburb of Grangegorman. It formed part of the HSE mental health services of Dublin North East. Its catchment area is North West Dublin. Since the official opening of the Richmond Lunatic Asylum in 1815 the Grangegorman site has continuously provided institutional facilities for the reception of the mentally ill until the present day.

The majority of the buildings historically associated with the hospital have been either demolished, fallen into disrepair or closed down. There are currently five wards still in use in the facility which are all situated in old buildings and which provide eighty-four beds for psychiatric patients. In the 2008 Report of the Inspector of Mental Health Services it was recommended that acute admissions to the secure units 3A and 3B should cease due to their unsuitability and all admissions should be redirected to the new purpose built unit at Connolly Hospital, Blanchardstown, Dublin. This new acute psychiatric unit was finally opened in Connolly Hospital on 29 November 2010 allowing for the commencement of the transfer of patients from St. Brendan's to Blanchardstown. This is part of a process that will see all the old units at St. Brendan's retired as psychiatric facilities. However, this does not signal the end of the use of the site for the provision of mental health services. As part of the Grangegorman Development Plan, where a large portion of the site of the old hospital will be used to develop a new Dublin Institute of Technology campus, new modern psychiatric facilities are to be provided for the HSE mental health services for the region.

St. Brendan's hospital is closed and no longer operates. A new 'state of the art' 'Phoenix care centre' has been developed situated in the Grangegorman area. This opened in March 2013 and comprises of 54 bedrooms and ensuites, recreational rooms, clinical rooms, administration areas, seclusion rooms and therapy gardens.