Boundary Islet, historically known as North East Islet, is a Hogan Groupislet of less than two hectares (4.9 acres) that straddles the border of the Australian states of Victoria and Tasmania. The islet is Tasmania's only land boundary, and at 85 metres (279 ft) long, it is the shortest land border between any Australian state or territory.
It is located at latitude 39°12' S, approximately 56 kilometres (35 mi) east of the southernmost point of mainland Victoria. The boundary between Victoria and Tasmania is a parallel similarly at latitude 39°12'. The position of the island was surveyed in 1801 by Captain John Black, who erred in placing the islet further north than it is. It was later found that the border at 39°12' S actually passed through the islet.