New Territories (abbreviated to NT or N.T.) (traditional Chinese: jyutping: san¹gaai³) is one of the three main regions of Hong Kong, alongside Hong Kong Island and the Kowloon Peninsula. It makes up 86.2% of Hong Kong's territory. Historically, it is the region described in The Convention for the Extension of Hong Kong Territory. According to that the territories comprise the mainland area north of the Boundary Street of Kowloon Peninsula and south of the Sham Chun River which is the border between Hong Kong and Mainland China, as well as over 200 outlying Islands including Lantau Island, Lamma Island, Cheung Chau, and Peng Chau in the territory of Hong Kong.

Later, after New Kowloon was defined from the area between the Boundary Street and the Kowloon Ranges spanned from Lai Chi Kok to Lei Yue Mun, and the extension of the urban areas of Kowloon, New Kowloon was gradually urbanised and absorbed into Kowloon. In modern times New Kowloon is almost always considered part of Kowloon and instead of the New Territories – except statutorily.

Hence, the New Territories now comprises only the mainland north of the Kowloon Ranges and south of the Sham Chun River, as well as the Outlying Islands. It comprises an area of 952 km² (368 sq mi).Nevertheless, New Kowloon has remained statutorily part of the New Territories instead of Kowloon.

The New Territories were leased from Qing Dynasty|Qing] China to the United Kingdom in 1898 for 99 years in the Second Convention of Peking (The Convention for the Extension of Hong Kong Territory). Upon the expiration of the lease, sovereignty was transferred to the People's Republic of China in 1997, together with the Qing ceded territories of Hong Kong Island and Kowloon Peninsula.

In 2011, the Population of the New Territories was recorded at 3,691,093 with a population density of 26,000 per square kilometre (67,000 per square mile.