A gold nugget is a naturally occurring piece of native gold. Watercourses often concentrate and grow the nuggets. Nuggets are recovered by placer mining, but they are also found in residual deposits where the gold-bearing veins or lodes are weathered. Nuggets are also found in the tailings piles of previous mining operations, especially those left by gold mining dredges.

Many nuggets are formed by cold welding of smaller particles and fragments in streams and rivers. Gold's softness makes it prone to welding under impact or hammering loads, such as those produced at waterfalls and in rapids. There is no oxide surface layer to inhibit adhesion between gold flakes. So when pieces of gold hit one another under pressure, they may join into a bigger piece.^{[citation needed][dubious – discuss]} Some nuggets may have been present in massive form in the original vein before erosion, often showing signs of abrasive polishing by stream action. (Other precious metals such as platinum form nuggets in the same way.) The exceptional ductility and malleability of gold means brittle fracture is impossible.

Gold Bug is a (sometimes pejorative) term used to describe investors who are very bullish on buying the commodity gold (XAU - ISO 4217). It can also be used to refer to a person who opposes or criticizes the use of fiat currency and supports a return to the use of the Gold Standard or some other currency system based on the value of gold and other hard assets. A third use is to refer to someone who considers one commodity, usually gold, "the appropriate measure of wealth, regardless of the quantity of other goods and services that it can buy".

The term was popularized in the 1896 US Presidential Election, when William McKinley supporters took to wearing gold lapel pins, gold neckties, and gold headbands in a demonstration of support for gold against the "silver menace", though the term's original use may have been in Edgar Allan Poe's 1843 story "The Gold-Bug," about a cryptographic treasure map.