Although exact dates have yet to be confirmed by hard evidence, it is widely believed that a Count named Camillo Negroni was the first person to ever order the Negroni.
Count Negroni went to a bar in Italy and instead of ordering his usual Americano (Soda water, Campari, and Sweet Vermouth), he requested the bartender to stiffen up his drink a bit by replacing the soda water with Gin and the rest is history.
A traditional Negroni is made up of equal parts Gin, Campari, and Sweet Vermouth with an orange twist for garnish. Despite the Sweet Vermouth, the Negroni falls on the bitter spectrum of cocktails thanks to the Campari. The Sweet Vermouth gives the Negroni a slightly sweet flavor with notes of sweet fruit, Mediterranean spices, and a bit of bitterness.
The Gin gives the cocktail notes of juniper and freshness that is needed to lighten the Negroni. Most notably, the Campari gives the Negroni its famous bitter taste with notes of fruit and spices like cloves. The Negroni is known to be a potent cocktail and is advised to be consumed leisurely.