Leoni was born in Rome and moved to Padua at the age of 5. He began playing football with Vigontina before moving to Cittadella, and finished his youth development at Padova.[3] He made his senior and professional debut with Padova as a late substitute in a 3–2 Serie C win over AlbinoLeffe on 19 March 2023 at the age of 16 years and 3 months, making him the youngest professional footballer in Italy that season.[4] On 1 February 2024, he joined Sampdoria on loan until June 2026 with an option to buy for €1.5 million.[5]
On 25 June 2024, Leoni signed a three-year contract with Sampdoria.[6]
Leoni is a youth international for Italy, having been called up to the Italy U17s in March 2024.[8]
Playing style
A tall, strong and ambidextrous centre-back, Leoni can play as in the centre or right side of a three-man defense. He is very agile and skilled with his head. He is also a modern defender who is skilled in the build up game, and in covering spaces tactically.[5]