The most populous city in Oceania is Sydney, Australia. With a population of over 5 million people, it is the largest city in Australia and the most populous city in Oceania. It is located on the east coast of Australia and is the state capital of New South Wales. Sydney is a major global city and is known for its iconic landmarks such as the Sydney Opera House and the Sydney Harbour Bridge. It is also home to many cultural institutions and is a popular tourist destination.