The lieutenant governor of New Brunswick is the representative in New Brunswick of the monarch, who operates distinctly within the province but is also shared equally with the ten other jurisdictions of Canada, as well as the other Commonwealth realms and any subdivisions thereof, and resides predominantly in his oldest realm, the United Kingdom. The lieutenant governor of New Brunswick is appointed in the same manner as the other provincial viceroys in Canada and is similarly tasked with carrying out most of the monarch's constitutional and ceremonial duties. The current lieutenant governor is Brenda Murphy, since September 8, 2019.

By the arrangements of the Canadian federation, Canada's monarchy operates in New Brunswick as the core of the province's Westminster-style parliamentary democracy. As such, the Crown within New Brunswick's jurisdiction is referred to as the Crown in Right of New Brunswick, His Majesty in Right of New Brunswick, or the King in Right of New Brunswick. The Constitution Act, 1867, however, leaves many royal duties in the province specifically assigned to the sovereign's viceroy, the lieutenant governor of New Brunswick, whose direct participation in governance is limited by the conventional stipulations of constitutional monarchy.