Which spirit is the base of a Moscow Mule?

The base spirit of a Moscow Mule is vodka.

A Moscow Mule combines vodka with ginger beer and lime juice, usually over ice. It is commonly served in a copper mug, whose cold surface and distinctive appearance became strongly associated with the drink. The cocktail is a type of buck, a mixed drink built around a spirit, citrus, and ginger beer.

The Moscow Mule emerged in the United States in the early 1940s. Its creation is often connected with John Martin of the Heublein company, vodka executive Rudolph Kunett, and Jack Morgan, owner of the Cock ’n’ Bull restaurant and producer of ginger beer. The drink helped promote both Smirnoff vodka and ginger beer at a time when vodka was still unfamiliar to many American drinkers.

The copper mug is traditional, but an unlined copper vessel can react with acidic drinks such as lime juice. Food-safety guidance therefore favors mugs lined with stainless steel or another protective material. Substituting bourbon, rum, gin, or tequila creates a named variation rather than a classic Moscow Mule.