Whiskey Sour is an American cocktail that originated sometime in the 1870s. This cocktail classic is composed of whiskey or bourbon, sugar or Gomme syrup, lemon juice, and optionally an egg white. It is believed that the original version did not include an egg white, but it was added later to give the drink a smoother texture.

Modern recipes often leave it out or list it as an optional ingredient. If an egg white is added to the mix, the drink is often referred to as Boston Sour, and if red wine is included in the cocktail, it is then called New York Sour. In some versions, sugar syrup can be replaced with grenadine syrup, while other versions add both lemon juice and orange juice.

Whiskey Sour is a shaken cocktail typically served on the rocks in an old-fashioned glass, usually garnished with a Maraschino cherry and orange zest or half of an orange slice.