Which Australian capital city had a 2021 GCCSA population of 5,259,764? Sydney. The figure is the Australian Bureau of Statistics estimate for Greater Sydney, the city’s Greater Capital City Statistical Area, at 30 June 2021.
GCCSA is a statistical boundary designed to represent a capital city and its surrounding metropolitan area, not merely the central local-government area called the City of Sydney. That distinction matters: the City of Sydney itself contains only a small fraction of Greater Sydney’s residents, while the broader region stretches across many councils and suburbs.
Sydney is the capital of New South Wales and Australia’s most populous capital city. Melbourne was the nearest comparison in 2021, but its GCCSA population was below Sydney’s. Population totals can differ between a census count, estimated resident population and urban-area definitions, so the boundary and date should always be checked when comparing Australian cities.