
The Department of Defence is the department of the Government of Ireland that is responsible for preserving peace and security in Ireland. The department is led by the Minister for Defence.

The Army Reserve (AR) is the reserve land component of the Irish Defence Forces. It is the second line reserve of the Irish Army. The Army Reserve involves active military service on a part-time basis, and is one of two elements of the Reserve Defence Forces, the other element being the Naval Service Reserve (NSR).

The Defence Forces are the armed forces of Ireland. They encompass the Army, Air Corps, Naval Service and Reserve Defence Forces.

The Directorate of Military Intelligence is the military intelligence branch of the Defence Forces, the Irish armed forces, and the national intelligence service of Ireland. The organisation has responsibility for the safety and security of the Irish Defence Forces, its personnel, and supporting the national security of Ireland. The directorate operates domestic and foreign intelligence sections, providing intelligence to the Government of Ireland concerning threats to the security of the state and the national interest from internal and external sources.

Ireland and the North Atlantic Treaty Organization have had a formal relationship since 1999, when Ireland joined as a member of the NATO Partnership for Peace (PfP) programme and signed up to NATO's Euro-Atlantic Partnership Council (EAPC). To date, Ireland has not sought to join as a full NATO member due to its traditional policy of military neutrality.

The Irish Red Cross Society is the National Red Cross Society for the Republic of Ireland. The society was formally established on 6 July 1939 under the Red Cross Act 1938. It is affiliated to the International Federation of Red Cross and Red Crescent Societies. The society is organised on a voluntary basis. In Ireland, its activities include mountain rescue, first aid education of the public, the provision of first aid and ambulance services at public events, as well as other community services for older people, carers, migrants and prisoners. Outside Ireland, the society provides relief and humanitarian services in response to natural disasters and in regions of conflict.

This is a list of Irish military installations occupied by the Defence Forces in the Republic of Ireland by province and overseas.

The Minister for Defence is the senior minister at the Department of Defence in the Government of Ireland. The current Minister for Defence is Simon Coveney, TD. He is also Minister for Foreign Affairs.

The Naval Service Reserve (NSR) is the reserve force of the Irish Naval Service. It is one of two elements of the Reserve Defence Forces (RDF) of the Irish Defence Forces, the other element being the Army Reserve (AR). The NSR was established on 1 October 2005 to replace and reorganise the previous naval reserve organisation, An Slua Muirí, which in turn replaced the fore-runner Maritime Inscription founded in 1940 to act as a Port Control authority during The Emergency (WWII). Originally formed at Dublin's Alexandra Basin, its headquarters was in Portobello barracks, now known as Cathal Brugha Barracks.

The Office of Emergency Planning (OEP) is a civil/military body within Ireland's Department of Defence responsible for the co-ordination and oversight of emergency planning between state agencies. It is answerable to the Minister for Defence.

The Ordnance Corps (ORD) is a combat support corps of the Irish Army, a branch of the Defence Forces, that has logistical and operational responsibility for military ordnance in Ireland. The logistical role of the Army Ordnance Corps is to provide technical support to the Defence Forces for the procurement, storage, distribution, inspection, maintenance, repair and disposal of all items of ordnance equipment. The operational role of the Ordnance Corps is to train personnel for and provide the state's bomb disposal capability.

The Reserve Defence Forces (RDF) are the combined reserve components of the Irish Defence Forces. The RDF is organised into the First Line Reserve (FLR) and an active Second Line Reserve. The First Line Reserve comprises former members of the Permanent Defence Forces (PDF) and the Second Line Reserve comprises the Army Reserve (AR) and Naval Service Reserve (NSR).