Ma Shi Chau (Chinese: 馬屎洲 Cantonese: ma5 si2 zau1) is one of the 235 islands of Hong Kong, under the administration of Tai Po District. It is located in Tolo Harbour (吐露港), which is in the northeast of the New Territories (新界).
It is connected with Yim Tin Tsai by a narrow strip of land that is only accessible when the tide is low.
Its name literally means "horse excrement island".
Ma Shi Chau is part of Ma Shi Chau Special Area.