The Negroni is said to have evolved from the Milano-Torino, invented in the 1860s at the Caffe Camparino in Milan, Italy. The Milano-Torino, consisting of red bitter and sweet vermouth, was popular with Americans, who often asked for the drink to be modified with a splash of soda water. This is how the drink that was once the Milano-Torino evolved to the Americano.

Back in 1919, this classic drink maintained its reputation as one of the most popular drinks of all time. In addition, the Negroni continued to evolve. According to legend, the Negroni originated in Caffe Casoni, located in the city of dreams, also known as Florence, Italy. It has been said that the widely popular aperitif was commissioned by the London based Count Camillo Negroni who asked his friend Forsco Scarselli – a bartender at the aforementioned restaurant – to improve his Americano, which was apparently his favorite drink. Scarselli made a commitment, replacing one of the main components of the drink with a stronger ingredient, ultimately swapping the traditional soda water for gin while replacing the traditional lemon garnish with orange so the two drinks wouldn't be confused.

After the explosive popularity of the soon-to-be-named Negroni, the Count's family built on their success by founding the Negroni distillery in Treviso, Italy, that same year. Their company produced a standard version of the cocktail, which they called the Antico Negroni. Due to the never-ending success of the Negroni, the renowned European distillery is still in operation today.

Another contender for the true inventor may have been a French military general rather than an Italian aristocrat. Commander Pascal-Olivier de Negroni is said to have invented the drink decades earlier, either in a Parisian officers' club or while stationed in West Africa as a gift for his new bride.