The South Island is the largest of the three major islands of New Zealand by surface area, the others being the smaller but more populous North Island and Stewart Island. It is bordered to the north by Cook Strait, to the west by the Tasman Sea, to the south by the Foveaux Strait and Southern Ocean, and to the east by the Pacific Ocean. The South Island cover…The South Island is the largest of the three major islands of New Zealand by surface area, the others being the smaller but more populous North Island and Stewart Island. It is bordered to the north by Cook Strait, to the west by the Tasman Sea, to the south by the Foveaux Strait and Southern Ocean, and to the east by the Pacific Ocean. The South Island covers 150,437 square kilometres, making it the world's 12th-largest island, constituting 56% of New Zealand's land area. At low altitudes, it has an oceanic climate. The most populous cities are Christchurch, Dunedin, Nelson and Invercargill.