Australia's most populous city is Sydney, which is located in the state of New South Wales. It is the largest and most populous city in Australia, with a population of over 5 million people. Sydney is a major global city and is known for its iconic landmarks such as the Sydney Opera House and the Harbour Bridge. It is also home to many cultural attractions, including the Royal Botanic Gardens and the Art Gallery of New South Wales. Sydney is a popular tourist destination and is renowned for its vibrant nightlife and diverse range of restaurants.