Sydney, Australia's largest city, has transformed dramatically since its humble beginnings in 1788, when the population numbered less than 1,000. By 1798, following the arrival of convicts, the population had surged to nearly 3,000, and it has continued to grow ever since. The 2021 census recorded Greater Sydney's population at a staggering 5,231,150, with projections indicating it could reach between 8 and 8.9 million by 2061. Despite this growth, Melbourne is anticipated to surpass Sydney as the nation’s most populous city by 2030.

The demographics of Sydney reflect a rich tapestry of cultural diversity. The median age of residents is 37, with 14.8% of the population aged 65 or older. Nearly half (48.6%) of the city's residents are married, while 36.7% have never been married. Family structures are equally varied, with 49.0% of families being couples with children, 34.4% couples without children, and 14.8% consisting of single-parent families.

Ancestry and immigration play a vital role in shaping Sydney's identity. As of the 2021 census, 40.5% of the population was born overseas, with Mainland China, India, and England being the most common countries of birth. The leading ancestries include English (21.8%), Australian (20.4%), and Chinese (11.6%). Sydney is home to a significant Chinese Australian community, highlighted during vibrant celebrations like Chinese New Year in Chinatown.

Linguistically, Sydney is also diverse, with 42% of households speaking a language other than English. The most prevalent languages include Mandarin, Arabic, and Cantonese. Religiously, Christianity remains the dominant faith, representing 46% of the population, followed by those identifying as non-religious (30.3%). Islam and Hinduism are notable non-Christian faiths in the city.

Crime in Sydney is relatively low, ranking as the fifth safest city globally in 2019. However, drug-related issues persist, particularly with methamphetamine use. In recent years, measures such as lockout laws were implemented to address alcohol-fueled violence but were repealed in early 2020.

Overall, Sydney's demographics illustrate a dynamic and evolving urban environment, characterized by its multicultural heritage, youthful population, and an ever-changing landscape of challenges and opportunities.