Invented circa 1919 in Florence, Italy for Camillo Negroni, a Florentine Count who had recently returned to Italy from America, where he had spent time as a cowboy in the old west and as a gambler in New York.
1 oz dry gin
1 oz Campari
1 oz sweet vermouth
1 oz fizz water (optional)
Combine ingredients in a rocks glass containing ice and stir. Orange peel garnish.