Hong Kong Island is an island in the southern part of Hong Kong. It has a population of 1,289,500 and its population density is 16,390/km2, as of 2008. The island had a population of about 3,000 inhabitants scattered in a dozen fishing villages when it was occupied by the United Kingdom in the First Opium War (1839–1842). In 1842, the island was formally ceded in perpetuity to the UK under the Treaty of Nanking and the City of Victoria was then established on the island by the British Force in honour of Queen Victoria.

The Central area on the island is the historical, political and economic centre of Hong Kong. The northern coast of the island forms the southern shore of the Victoria Harbour, which is largely responsible for the development of Hong Kong due to its deep waters favoured by large trade ships.

The island is home to many of the most famous sights in Hong Kong, such as "The Peak", Ocean Park, many historical sites and various large shopping centres. The mountain ranges across the island are also famous for hiking.

The northern part of Hong Kong Island, together with Kowloon and Tsuen Wan New Town, forms the core urban area of Hong Kong. Their combined area is approximately 88.3 square kilometres (34.1 square miles) and their combined population (that of the northern part of the island and of Kowloon) is approximately 3,156,500, reflecting a population density of 35,700/km2 (91,500/sq. mi.).

The island is often referred to locally as "Hong Kong side" or "Island side". Suffix "side" applied to other locations (e.g. China-side and Kowloon Walled City-side), the sole remnant of which is "Kowloon side" when indicating the two sides of the harbour. The form was once more common in Britain than now, such as south/Surrey-side and endures in British placenames like Cheapside, Tyneside, and Teesside, not all of which have an obvious watercourse or boundary.