Neutral grain spirit (also called pure grain alcohol (PGA) or grain neutral spirit (GNS)) is a clear, colorless, flammable liquid that has been distilled from a grain-based mash to a very high level of ethanol content. The term neutral refers to the spirit's lacking the flavor that would have been present if the mash ingredients were distilled to a lower level of alcohol purity, and also lacking any flavoring added to it after distillation (as is done, for example, with gin). Other kinds of spirits, such as whisky, are distilled to a lower alcohol percentage in order to preserve the flavor of the mash.

The mash from which neutral grain spirit is produced can be any type or mixture of cereal grains.

As a defined standard of identification under U.S. law, "neutral spirits" or "neutral alcohol" are distilled spirits produced from any material at or above 95% alcohol by volume. Such a product made from grain is "grain neutral spirit," while such a spirit made from grapes is called "grape neutral spirit," and so on. When the term is used in an informal context rather than as a term of U.S. law, any distilled spirit of high alcohol purity (e.g., 170 proof or higher) that does not contain added flavoring may be referred to as neutral alcohol.

The purity of neutral grain spirit has a practical limit of 190 proof because a mixture of ethanol and water becomes an azeotrope at 95.6% ABV (191.2 proof).

Neutral grain spirit is only one type of neutral spirit (also called neutral alcohol). Neutral alcohol can also be produced from grapes, sugar beets, sugarcane, or other fermented plant material. In particular, large quantities of neutral alcohol are distilled from wine, a product that is referred to as vinous alcohol.