Sydney is the capital city of the state of New South Wales and the most populous city in Australia. Located on Australia's east coast, the metropolis surrounds Sydney Harbour and extends about 80 km (50 mi) from the Pacific Ocean in the east to the Blue Mountains in the west, and about 80 km (50 mi) from the Ku-ring-gai Chase National Park and the Hawkesbury River in the north and north-west, to the Royal National Park and Macarthur in the south and south-west.^[5] Greater Sydney consists of 658 suburbs, spread across 33 local government areas. Residents of the city are colloquially known as "Sydneysiders".^[6] The estimated population in June 2023 was 5,450,496,^[1] which is about 66% of the state's population.^[7] The city's nicknames include the "Emerald City" and the "Harbour City".^[8]

Aboriginal Australians have inhabited the Greater Sydney region for at least 30,000 years, and their engravings and cultural sites are common. The traditional custodians of the land on which modern Sydney stands are the clans of the Darug, Dharawal and Eora peoples.^[9] During his first Pacific voyage in 1770, James Cook charted the eastern coast of Australia, making landfall at Botany Bay. In 1788, the First Fleet of convicts, led by Arthur Phillip, founded Sydney as a British penal colony, the first European settlement in Australia.^[10] After World War II, Sydney experienced mass migration and by 2021 over 40 per cent of the population was born overseas. Foreign countries of birth with the greatest representation are mainland China, India, the United Kingdom, Vietnam and the Philippines.^[11]

Despite being one of the most expensive cities in the world,^[12][13] Sydney frequently ranks in the top ten most liveable cities.^[14][15][16] It is classified as an Alpha city by the Globalization and World Cities Research Network, indicating its influence in the region and throughout the world.^[17][18] Ranked eleventh in the world for economic opportunity,^[19] Sydney has an advanced market economy with strengths in education, finance, manufacturing and tourism.^[20][21] The University of Sydney and the University of New South Wales are ranked equal 19th in the world.^[22]

Sydney has hosted major international sporting events such as the 2000 Summer Olympics. The city is among the top fifteen most-visited,^[23] with millions of tourists coming each year to see the city's landmarks.^[24] The city has over 1,000,000 ha (2,500,000 acres) of nature reserves and parks,^[25] and its notable natural features include Sydney Harbour and Royal National Park. The Sydney Harbour Bridge and the World Heritage-listed Sydney Opera House are major tourist attractions. Central Station is the hub of Sydney's suburban rail and light rail networks, with metro platforms under construction. The main passenger airport serving the city is Kingsford Smith Airport, one of the world's oldest continually operating airports.