Triple sec, originally Curaçao triple sec, is a variety of Curaçao liqueur, an orange-flavoured liqueur made from the dried peels of bitter and/or sweet oranges.

Triple sec may be consumed neat as a digestif or on the rocks, but it is more often used as an ingredient in a variety of cocktails, such as sangria, margarita, Kamikaze, White Lady, Long Island Iced Tea, Sidecar, Skittle Bomb, Corpse Reviver #2, and Cosmopolitan.

The Combier distillery claims that triple sec was invented between 1834 and 1848 by Jean-Baptiste Combier in Saumur, France. However, Combier was more famous for its élixir Combier, which contained orange and many other flavorings.

Cointreau, on the other hand, claims that its orange liqueur was formulated in 1849.

Triple sec was widely known by 1878: at the Exposition Universelle of 1878 in Paris, several distillers were offering "Curaçao [sic] triple sec", as well as "Curaçao doux".