What is the main ingredient in a classic Martini?

The classic Martini primarily features gin as its main ingredient. A traditional Martini is known for its simplicity and its distinct flavor profile, which is predominantly derived from gin. The spirit contributes herbal and aromatic qualities that define the cocktail.

While dry vermouth is often used as a minor component to complement gin in a classic Martini, it is not the main ingredient; instead, it serves to enhance the gin's flavor. Sweet vermouth and whiskey are not typically associated with a classic Martini, as sweet vermouth is generally used in cocktails like the Manhattan, and whiskey changes the nature of the drink entirely. Thus, the essence of a classic Martini lies in its gin foundation, making it the defining ingredient of this iconic cocktail.