The Nerazzurri have signed the 25-year-old Torino defender for an undisclosed fee on a four-and-a-half year contract.
The 25-year-old has been the mainstay of the team which has been performing surprisingly well in Serie A this term, having scored three goals in 14 appearances as Giampiero Ventura's side sits sixth.
D'Ambrosio has now sealed a move to San Siro, having signed a deal which expires in the summer of 2018.
"Danilo D'Ambrosio is now an Inter player," a club statement read.
"The relevant documentation was submitted to the Lega Serie A offices this morning, confirming the defender's move from Torino to the Nerazzurri. The Neapolitan, 25, has signed a deal until 30 June 2018."
The former Italy Under-21 international started his career with Potenza and made the move to Turin in 2010 after a spell with Juve Stabia.