The Campari Negroni is a cocktail named after Count Camillo Negroni.
One evening, in 1919, Count Negroni ordered an Americano, but a little stronger than usual.

He got his Americano with gin instead of soda and so the new cocktail was born.

The Negroni was invented in Florence, Italy in 1919 by Count Camillo Negroni when he asked his barman to replace the soda water in his Americano cocktail (Campari, Sweet Vermouth, Soda) with gin.