What is the base spirit in a traditional Old Fashioned?

The base spirit in a traditional Old Fashioned is Bourbon or Rye whiskey. The Old Fashioned cocktail is one of the oldest known whiskey cocktails, dating back to the early 19th century. Its classic recipe revolves around the rich, complex flavors of bourbon or rye, which are complemented by the addition of sugar, bitters, and a twist of citrus peel, typically orange.

Bourbon provides a sweet, smooth profile with notes of caramel and vanilla, while rye offers a spicier, more robust flavor. This foundational spirit is integral to the cocktail's identity, as it sets the tone for the drink and interacts harmoniously with the other ingredients. The combination of these components enhances its overall depth, making Bourbon or Rye whiskey the essential base spirit for this timeless drink.