The minister of state at the Department of Defence (Irish: Aire Stáit ag an Roinn Cosanta) is a junior ministerial post in the Department of Defence of the Government of Ireland who performs duties and functions delegated by the minister for defence. Although the position has often been held jointly with that of the post of Minister of State at the Department of the Taoiseach with responsibility as Government Chief Whip, which entitles the office-holder to regularly attend meetings of cabinet, the position of minister of state does not itself hold cabinet rank. The title was first used on 1 January 1978, replacing the position of parliamentary secretary to the minister of defence. The minister of state at the Department of Defence is a member of the Council of Defence.
The current minister of state is Thomas Byrne, TD, who was appointed in January 2025. Byrne is also Minister of State for European Affairs.