Sai Kung District is one of the 18 districts of Hong Kong. The district comprises the southern half of the Sai Kung Peninsula, the Clear Water Bay Peninsula in the New Territories and a strip of land to the east of Kowloon. Areas in the district include Sai Kung Town, Hong Kong UNESCO Global Geopark, Tseung Kwan O and over 70 islands of different sizes. The administrative centre had been located in Sai Kung Town until the Sai Kung District Office was relocated to Tseung Kwan O recently. The district's population is concentrated in Tseung Kwan O, as of 2011. In 2011, the district was the third youngest district, with a median age of 39.3. Known as the "back garden of Hong Kong", Sai Kung has been able to retain its natural scenery. Many traditional customs and cultures are still retained in the rural villages.

The modern geopolitical entity of Sai Kung District was formed after World War II. Settlements existed in the area prior to the signing of the Convention for the Extension of Hong Kong Territory, which ceded the area to the colony of Hong Kong from the Qing Empire in 1898. Those ceded areas are now collectively known as the New Territories and New Kowloon.

According to Professor David Faure, unlike other villages of the New Territories, villages in Sai Kung did not form any yeuk (Chinese: 約), a kind of inter-village alliances in the 19th century in the Qing dynasty.

Under the colonial rule, villages in Sai Kung were grouped under Tung Yeuk (also known as Tung Hoi Yeuk; Chinese: 東海約; lit. 'East Sea yeuk') in 1898.

Soon after, the district office of New Territories was established. The New Territories was divided into Northern and Southern District (both not the same as the modern day districts of HK) and New Kowloon in the 1920s. The area around the modern day Sai Kung Town was under the District Office North until 1947, which the area was under the administration of the Southern District (not the same as modern day Southern District) from 1947. The Southern District was under further reform since 1957.

After the end of World War II (the author did not state the exact year, however), the New Territories was divided into 8 sub-divisions, one of which was named after Sai Kung. Such sub-divisions was soon abolished. The North and South District Office were merged to form New Territories Administration, a department of the executive branch of the government, in 1948–1952, which has 3 sub-divisions: Tai Po (covers some of the area of the former Northern District), Yuen Long and Southern District. Sai Kung was under the aforementioned Southern District. Tsuen Wan District Officer was established in 1959 and craved out from the Southern District. The Southern District at that time only administrated the modern-day Sai Kung District and Islands District. A branch office of the Southern District was also established in Mui Wo in 1957, which now belongs to Lantau Island of the Islands District. It was reported that circa the early 1960s, the Southern District was further split into Sai Kung District and Islands District, but merged back in 1963.

By 1969, the New Territories Administration had 7 district offices, of which one was named after Sai Kung.

In 1977, the Hong Kong Governor announced to establish District Advisory Boards to invite locals to become advisors. Although Sai Kung locals, as well as other rural villages of the New Territories, already established their chambers and voting representatives to Heung Yee Kuk, an advisory body to the colonial government, as early as the 1930s.