Colidio joins Inter's academy on a three-year contract.
The 17-year-old Argentine striker is believed to have cost around €6m.
He had been due to arrive in January 2018, when he'd turn 18 years old, but Inter announced today they have brought the matter forward.
The Nerazzurri received his international transfer and Colidio signed a three-year contract.
He will begin training with Stefano Vecchi's Primavera youth team.