Lion Island is an island that is located at the mouth to the Hawkesbury River in Broken Bay on the Central Coast of the state of New South Wales, Australia. The island is located just off Pearl Beach and is part of the Central Coast Council local government area. It is a descriptive name because it resembles a Sphinx, a mythical figure of a crouching lion.

Broken Bay, a semi-mature tide-dominated drowned valley estuary, is a large inlet of the Tasman Sea located about 50 kilometres (31 mi) north of Sydney on the Central Coast of New South Wales, Australia; being one of the bodies of water that separate greater Metropolitan Sydney from the Central Coast. Broken Bay is the first major bay north of Sydney Harbour in the state capital of Sydney.