Larnach Castle is a mock castle on the ridge of the Otago Peninsula within the limits of the city of Dunedin, New Zealand, close to the small settlement of Pukehiki. It is one of a few houses of this scale in New Zealand. The house was built by prominent entrepreneur and politician, William Larnach. The Castle is now privately owned by the Barker Family, and operated as a tourism destination.
The Castle and Grounds are open daily to members of the public. The Larnach Castle gardens are one of only five gardens nationwide to have been given the rating of "Garden of International Significance" by the New Zealand Gardens Trust. These were the first gardens in the South Island to receive the title.