A dry county is a county in the United States whose government forbids the sale of alcoholic beverages. Some prohibit off-premises sale, some prohibit on-premises sale, and some prohibit both. Hundreds of dry counties exist across the United States, almost all of them in the South. A number of smaller jurisdictions also exist, such as cities, towns and townships, which prohibit the sale of alcoholic beverages. These are known as dry towns, dry cities or dry townships.

Although the 21st Amendment repealed the prohibition of alcohol on the federal level, that Amendment also specifically prohibits the selling or production of alcohol in violation of state laws. Some states after the repeal passed local option laws granting counties and municipalities, either by popular vote or ordinance, the ability to decide for themselves whether to allow alcohol.

Many dry communities do not prohibit the mere consumption of alcohol, which could potentially cause a loss of profits and taxes from the sale of alcohol to their residents in "wet" (non-prohibition) areas. The rationale for maintaining prohibition on the local level often is religious in nature, as many Protestant Christian denominations discourage the consumption of alcohol by their followers (see Christianity and alcohol, sumptuary law, and Baptists and Bootleggers). While state law does not allow for dry counties, similar laws designed to restrict the sale and consumption of alcohol also are common in the mostly LDS (Mormon) state of Utah. Utah state law prohibits local jurisdictions from exercising control over liquor laws. An additional, more pragmatic intent of these laws often is to reduce alcohol consumption in that particular county (and the potential health, safety, and public order issues that can accompany it) by limiting the ease of acquiring it.