Long Island is an island in Fiordland

Fiordland

Fiordland is a geographic region of New Zealand that is situated on the south-western corner of the South Island, comprising the western-most third of Southland. Most of Fiordland is dominated by the steep sides of the snow-capped Southern Alps, deep lakes and its ocean-flooded, steep western valleys...

, in the southwest of New Zealand

New Zealand

New Zealand is an island country in the south-western Pacific Ocean comprising two main landmasses and numerous smaller islands. The country is situated some east of Australia across the Tasman Sea, and roughly south of the Pacific island nations of New Caledonia, Fiji, and Tonga...

's South Island

South Island

The South Island is the larger of the two major islands of New Zealand, the other being the more populous North Island. It is bordered to the north by Cook Strait, to the west by the Tasman Sea, to the south and east by the Pacific Ocean...

. It lies within Dusky Sound

Dusky Sound

Dusky Sound is a fiord on the south west corner of New Zealand, in Fiordland National Park.-Geography:One of the most complex of the many fjords on this coast, it is also one of the largest, 40 kilometres in length and eight kilometres wide at its widest point...

, to the southeast of Resolution Island

Resolution Island, New Zealand

Resolution Island is the largest island in Fiordland region of southwest New Zealand, covering a total of . It is the country's seventh largest island...

, and is separated from it and the South island mainland by Bowen Channel to the north, and from the South Island mainland by Cook Channel to the south.

Long Island is 12 kilometres (7.5 mi) in length and a maximum of 2 kilometres (1.2 mi) in width.