The region now known as Sydney has been inhabited for tens of thousands of years, primarily by Aboriginal Australians who migrated from Southeast Asia through northern Australia. Archaeological evidence, including flaked pebbles discovered in Western Sydney's gravel sediments, suggests human presence in the area dating back 45,000 to 50,000 years, with radiocarbon dating indicating consistent human activity from approximately 30,000 years ago. Before the arrival of British settlers, the Greater Sydney region was home to an estimated 4,000 to 8,000 Aboriginal people.

These early inhabitants thrived on a diet that included fishing, hunting, and gathering plants and shellfish. Coastal clans predominantly relied on seafood, while those in the hinterlands focused on forest animals and various plant sources. Distinctive tools and weapons made from stone, wood, plant materials, bone, and shell were utilized across different clans, each possessing unique body decorations, hairstyles, songs, and dances. Their rich ceremonial life was deeply intertwined with a belief system centered on ancestral, totemic, and supernatural beings, facilitating gatherings among different clans and language groups for significant events like initiation ceremonies, trade, marriages, and alliances.

The term 'Eora' was recorded by the earliest British settlers as an Aboriginal word meaning 'people' or 'from this place,' referring to the clans occupying the land with traditional boundaries. However, discussions regarding the specific affiliations and differences in language and cultural rites among these groups continue. The major groups included the coastal Eora people, the Dharug (Darug) people occupying the inland areas from Parramatta to the Blue Mountains, and the Dharawal people situated south of Botany Bay. On the outskirts of Sydney, languages such as Darginung and Gundungurra were spoken.

The first recorded encounter between Aboriginal Australians and British explorers occurred on April 29, 1770, when Lieutenant James Cook landed at Botany Bay, known to the Aboriginal people as Kamay. During this initial meeting, Cook and his crew encountered the Gweagal clan. Tensions arose when two Gweagal men opposed the landing, resulting in one being shot and wounded. Cook and his party spent a week at Botany Bay, gathering water, timber, fodder, and botanical specimens while attempting to establish relations with the local Aboriginal population, a goal that ultimately met with limited success.