(1836–39), organization of settlers from Van Diemen's Land (Tasmania) formed to purchase and develop the grazing land of the unsettled Port Phillip District (later the colony of Victoria) of southeastern Australia; its efforts precipitated the large-scale colonization of the area.

Originally consisting of 15 members who, in May 1835, had secured 600,000 acres (about 250,000 hectares) of grazing land from the Port Phillip Aborigines in exchange for an assortment of tools, clothes, and trinkets, the association was formally initiated in June 1835 as the Geelong and Dutigalla Association—after the Aboriginal names of its “purchased” tracts; it was known as the Port Phillip Association after April 1836. Each association member undertook to provide a certain number of sheep and herders for the evenly divided acres.

The organization's enterprise was successful but from the start illegal. It violated the British Colonial Office's 1829 Nineteen Counties order, which had limited the area open to settlement. Moreover, New South Wales governor Richard Bourke (1831–37), prompted by the association's action, voided all European-Aboriginal land deals in August 1835. Although the members of the association were in effect squatters, the government provided the association with a large indemnity for its trouble. By 1839 only three members remained; the name of the association was changed to the Derwent Company. This successor to the original enterprise dissolved in 1842.

While the Port Phillip Association itself was ill-fated, it led to large-scale and rapid colonization of the area, both from Van Diemen's Land and from New South Wales.