The 25-year-old has penned a five-year contract with the club, for a reported fee of €7m (£5.53m).
Bonaventura has been capped once by the Italian national side and scored eight goals in Serie A last season.
He has become the club's third signing of the week, following the arrivals of Fernando Torres and Marco van Ginkel on loan from Chelsea.
Restore Data
| Team | P | W | D | L | F | A | GD | PTS | |
| 1 | Atalanta BCAtalanta | 16 | 12 | 1 | 3 | 39 | 17 | 22 | 37 |
| 2 | Napoli | 16 | 11 | 2 | 3 | 24 | 11 | 13 | 35 |
| 3 | Inter Milan | 15 | 10 | 4 | 1 | 40 | 15 | 25 | 34 |
| 4 | Fiorentina | 15 | 9 | 4 | 2 | 28 | 11 | 17 | 31 |
| 5 | Lazio | 16 | 10 | 1 | 5 | 30 | 23 | 7 | 31 |
| 6 | Juventus | 16 | 6 | 10 | 0 | 26 | 12 | 14 | 28 |
| 7 | AC Milan | 16 | 7 | 5 | 4 | 25 | 16 | 9 | 26 |
| 8 | Bologna | 15 | 6 | 7 | 2 | 21 | 18 | 3 | 25 |
| 9 | Udinese | 16 | 6 | 2 | 8 | 19 | 25 | -6 | 20 |
| 10 | Empoli | 16 | 4 | 7 | 5 | 14 | 16 | -2 | 19 |
| 11 | Torino | 16 | 5 | 4 | 7 | 17 | 20 | -3 | 19 |
| 12 | Roma | 16 | 4 | 4 | 8 | 18 | 23 | -5 | 16 |
| 13 | Genoa | 16 | 3 | 7 | 6 | 13 | 24 | -11 | 16 |
| 14 | Lecce | 16 | 4 | 4 | 8 | 10 | 27 | -17 | 16 |
| 15 | Parma | 16 | 3 | 6 | 7 | 23 | 28 | -5 | 15 |
| 16 | Como | 16 | 3 | 6 | 7 | 18 | 28 | -10 | 15 |
| 17 | Hellas VeronaHellas Verona | 17 | 5 | 0 | 12 | 21 | 40 | -19 | 15 |
| 18 | CagliariCagliari | 16 | 3 | 5 | 8 | 15 | 26 | -11 | 14 |
| 19 | Monza | 16 | 1 | 7 | 8 | 14 | 21 | -7 | 10 |
| 20 | VeneziaVenezia | 16 | 2 | 4 | 10 | 15 | 29 | -14 | 10 |
| > Serie A Full Table | |||||||||
