私酒，是指非法生产（通常在自家酿造）的高酒精度的蒸馏酒。在西方主要是由玉米糊作为主要生产原料 。为避免被发现所以蒸馏通常在夜间进行，所以英语也用“月光”（Moonshine）一词来指代私酒。

由于禁酒令曾在美国实行，私酿的威士忌对于美国阿巴拉契亚山区人民非常重要。来自北爱尔兰的移民把自己老家的配方拿过来，从而成为了当地的一种传统。

中国在汉朝实行过短暂的酒类专卖之后，历朝历代都基本出现过酒类专卖或高酒税时期。由于民间的需求不会减少，这都促成了私酒酿造。宋朝由于实行相对严格的禁酒令，因此也是私酒酿造的高峰时期。

Moonshine, white lightning, mountain dew, hooch, homebrew, and white whiskey are terms used to describe high-proof distilled spirits that are generally produced illicitly. Moonshine is typically made with corn mash as the main ingredient. Liquor-control laws in the United States that prohibit moonshining, once consisting of a total ban under the 18th Amendment to the United States Constitution, now center primarily on evasion of revenue taxation on spiritous and/or intoxicating liquors, and are enforced by the Bureau of Alcohol, Tobacco, Firearms and Explosives of the United States Department of the Treasury; such enforcers of these laws are known by the often derisive nickname of "revenooers".