Port Shelter, known in Cantonese as Ngau Mei Hoi (Chinese: 牛尾海; Jyutping: ngau4 mei5 hoi2; Cantonese Yale: ngàuh méih hói), is a harbour south of Sai Kung Peninsula in Hong Kong. The water body connects to Inner Port Shelter (known in Cantonese as Sai Kung Hoi; Chinese: 西貢海; Jyutping: sai1 gung3 hoi2; Cantonese Yale: sāi gung hói), as well as Hebe Haven (白沙灣), Rocky Harbour (糧船灣海) and other water body. Outer Port Shelter, is situated at the mouth of the harbour.

The boundary of Port Shelter has different definition according to different sources. Publication of the U.S. Hydrographic Office, had stated the western shores of Keui Island (now known as Kau Sai Chau) and Jin Island, as well as eastern and north-east shores of the mainland area (now HKUST, Tseung Kwan O New Town and Clear Water Bay Peninsula), were the boundaries of Port Shelter. The Hydrographic Office also stated the entrance of the harbour lies between Lung Ha Wan (龍蝦灣; located in Clear Water Bay Peninsula) and [a] Peaked Rock [sic], with a width of about 1.5 miles (2.4 km). Earlier publication of the Office, had stated the peaked rock is located 300 yards (270 m) south of Jin Island. The rock was 44 feet (13 m) above water at that time.

Inner Port Shelter is located near the head of Port Shelter, while Hebe Haven was classified as an inlet in the western shore of Port Shelter. The entrance of Inner Port Shelter lies between Yingam Tow [sic] and a line of rocks that extended from Kiau To [sic], an islet (now spells as Kiu Tau; Chinese: 橋頭; Jyutping: kiu4 tau4; Cantonese Yale: kìuh tàuh). The islet itself is connected to Sharp Island (Kiu Tsui Chau; Chinese: 橋咀洲; Jyutping: kiu4 zeoi2 zau1; Cantonese Yale: kìuh jéui jāu) by a bank. The bank, or known as a sand levee or a tombolo, is part of the Hong Kong UNESCO Global Geopark.

While The Hydrographic Office's 1943 publication did not have the definition of Outer Port Shelter, H.K.'s Agriculture, Fisheries and Conservation Department had deployed artificial reef to the Outer Port Shelter in the 2000s. They defined the area by coordinates instead. Roughly, it is a triangular area between Steep Island, Basalt Island and the southern shore of Jin Island (known as Tiu Chung Chau in the publication).

Environmental Protection Department, partnered with local universities, also conducted water quality and phytoplankton research in the Port Shelter. In their research, they used a border definition of the area, which their Port Shelter includes Port Shelter proper, Inner and Outer Port Shelter as well as Hebe Haven, and is a bay that "bordered on its northernside by the Sai Kung Peninsula and on its west and southwestern sides by the Clear Water Bay Peninsula". They also found out that, some data point of their research, are obviously influenced by surface runoff and pollution loading from the surrounding catchment area.

These islands are considered within the boundary of the water body of the Port Shelter proper: The three largest islands were Kau Sai Chau, Jin Island and Sharp Island respectively.

Note: the book Southern District Officer Reports: Islands and Villages in Rural Hong Kong, 1910–60 also listed High Island, Town Island and Ninepin Group in their chapter "The Islands of Port Shelter". But the first two are located in Rocky Harbour, and the last one is outside the mouth of Outer Port Shelter.

These islands are considered within the boundary of the water body of Inner Port Shelter: