Sisters' Islands are two of the Southern Islands in Singapore and are located to the south of the main island of Singapore, off the Straits of Singapore. It can be reached via a boat ride from Marina South Pier or West Coast Pier.

Saint John's Island also known as St John's is an island in the Straits of Singapore located 6.5 km off the southern coast of Singapore. With an area of 0.41 km2 (0.16 sq mi), it is the largest of the Marine Park islands which also include the Sisters' Islands and Pulau Tekukor. St John's was colonised by the British along with mainland Singapore in the 19th century and was the site of a colonial quarantine centre. In the 20th century, the island served as a detention centre, drug rehabilitation centre and refugee settlement. Singapore gained independence under the Government of Singapore in the mid-20th century and maintained sovereignty over St John's. In the present day, the island has doubled as grounds for recreational facilities and aquaculture research and development facilities.