Lost River is a locality, in the Upper Lachlan Shire, within the Southern Tablelands of New South Wales, Australia.

There is a watercourse by the name of Lost River—a tributary of Wheeo Creek, in the Lachlan River catchment—that bisects the locality,[4] and forms a part of the boundary between the parishes.

However, the locality name, Lost River, also may have referred to an ancient watercourse, now in an elevated position as a result of geological processes.

The first directors of the company were business people from the region, including three jewellers, and a sapphire mine owner from near Inverell.

[18][16][19][21] Ancient sediments were mined by shaft and open-cut methods and then processed by sluicing, using water from the creek at the base of the hill, and then by gravity separation on two shaking screens.