The Thomson Dam is a major Clay core and rockfill embankment dam with a Uncontrolled, Ogee-shaped overflow weir and chute spillway across the Thomson River, located about 130 kilometres (81 mi) east of Melbourne in the West Gippsland region of the Australian state of Victoria.

Despite opposition from conservationists and farmers, plans for the dam were originally approved in late December 1975 to provide Melbourne with water security.

A dam on the Thomson River was preferred because the river had a large flow, high water quality and was elevated high enough to provide water to the upper Yarra system by gravity flow.

While there were minor rises in water levels occasionally, the Thomson Dam reached its all-time low of 16.2% on 3 July 2009.

[3] Heavy rainfall in 2010 and 2011 increased Melbourne's water storages to levels not seen for ten years.