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 Sai Kung Peninsula is a peninsula in the easternmost part of the New Territories in Hong Kong. Its name comes from Sai Kung Town in the central southern area of the peninsula. The southern part of the peninsula is administered by Sai Kung District, the north by Tai Po District and the northwest by Sha Tin District.