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.

A ria is a coastal inlet formed by the partial submergence of an unglaciated river valley. It is a drowned river valley that remains open to the sea.