Western Sydney is a major region of Sydney, Australia. It has a number of different definitions but one consistently used is the region composed of the 11 councils which until recently were all members of the Western Sydney Regional Organisation of Councils:

Western Sydney as defined by the WSROC region covers 5,800 square kilometres and had an estimated resident population as at 30 June 2008 of 1,665,673.

Western Sydney is also used to refer to the Greater Western Sydney region, which is the combination of Western Sydney as defined above and the Macarthur Region (also referred to as South-Western Sydney). As well as the 11 councils listed above, the GWS region includes Camden Council, Campbelltown City Council and Wollondilly Shire Council.

The NSW Government's Office of Western Sydney uses the broader Greater Western Sydney definition to refer to the region, which includes both WSROC and MACROC council areas.

Sydney ( /sɪdni/) is the most populous city in Australia and the state capital of New South Wales. Sydney is classified as an Alpha+ World City indicating its influence in the region and throughout the world.

Sydney is located on Australia's south-east coast of the Tasman Sea. As of June 2010, the greater metropolitan area had an approximate population of 4.6 million people. Inhabitants of Sydney are called Sydneysiders, comprising a cosmopolitan and international population.

The site of the first British colony in Australia, Sydney was established in 1788 at Sydney Cove by Arthur Phillip, commodore of the First Fleet as a penal colony. The city is built on hills surrounding Port Jackson which is commonly known as Sydney Harbour, where the iconic Sydney Opera House and the Harbour Bridge feature prominently. The hinterland of the metropolitan area is surrounded by national parks, and the coastal regions feature many bays, rivers, inlets and beaches including the famous Bondi Beach and Manly Beach. Within the city are many notable parks, including Hyde Park and the Royal Botanic Gardens.