IBA official recipe includes:
Components
30 ml – Gin
30 ml – Sweet Red Vermouth
30 ml – Campari
Preparation
Build in old fashioned glass over ice, garnish and serve.
* Notes – Standard garnish – Orange slice. Commonly served before dinner.
Enjoy ! ADB
The name “Negroni” is an Italian surname, and the drink is presumably named after some person of this name.