Hillsborough Castle is an official government residence in Northern Ireland. It is the official residence of the Secretary of State for Northern Ireland, and the official residence in Northern Ireland of the British monarch and other members of the British royal family when they visit the region, as well as a guest house for prominent international visitors.

The secretary of state for Northern Ireland, also referred to as the Northern Ireland secretary or SoSNI, is a secretary of state in the Government of the United Kingdom, with overall responsibility for the Northern Ireland Office. The incumbent is a member of the Cabinet of the United Kingdom.