Placer gold is a term that refers to gold found in a secondary deposit, usually in alluvial deposits such as sand and gravel in modern or ancient stream beds, or occasionally glacial deposits. Placer mining is the practice of separating heavily eroded minerals like gold from sand or gravel. The word placer is thought to have come from Catalan and Spanish, meaning a shoal or sandbar. The gold found in these secondary deposits is what is termed as placer gold. Placer gold deposits are usually not far off from where lode gold deposits are. The gold in hard rock is released during the weathering process and then carried off by glaciers or running water (streams, rivers, flood water) to someplace where it is deposited and concentrated in a placer deposit.

The simplest technique to extract gold from placer ore is panning. In panning, some mined ore is placed in a large metal or plastic pan, combined with a generous amount of water, and agitated so that the gold particles, being of higher density than the other material, settle to the bottom of the pan. The lighter gangue material such as sand, mud, and gravel are then washed over the side of the pan, leaving the gold behind. Other techniques used in placer mining include sluicing, dredging, and hydraulic mining.

Placer mining was famous in the context of several gold rushes, particularly the California Gold Rush and the Colorado Gold Rush, the Fraser Canyon Gold Rush, and the Klondike Gold Rush. Placer mining continues in many areas of the world as a source of diamonds, industrial minerals and metals, gems, platinum, and of gold.