A Cosmopolitan is a cocktail made with vodka, Cointreau or Triple Sec, cranberry juice, and fresh-squeezed lime juice or sweetened lime juice. Informally, it is referred to as a Cosmo.
According to the International Bartenders Association the original recipe is based on vodka citron, lemon-flavored vodka. The cosmopolitan is a relative of cranberry coolers like the Cape Codder. Though often presented far differently, the cosmopolitan also bears a likeness in composition to the kamikaze cocktail.
This origins of the cosmopolitan are somewhat disputed. It is likely that the drink was created independently by different bartenders since the 1970s. It is generally recognized that John Caine brought the drink to San Francisco around 1987 from the Midwest. The same year in Manhattan, the internationally recognized version of the cocktail was created by Toby Cecchini, based on a poorly described version of Cheryl Cook's creation. (Full article...)