| Mario Castellazzi | |
| Birth Date: | 9 November 1935 |
| Birth Place: | Finale Emilia, Italy |
| Death Place: | La Spezia, Italy |
| Position: | Midfielder |
| Years1: | 1953–1955 |
| Years2: | 1955–1957 |
| Years3: | 1957–1959 |
| Years4: | 1959–1960 |
| Years5: | 1960–1962 |
| Years6: | 1962–1963 |
| Years7: | 1963–1964 |
| Years8: | 1964–1968 |
| Clubs8: | Spezia |
| Caps2: | 44 |
| Caps3: | 55 |
| Caps4: | 6 |
| Caps5: | 51 |
| Caps6: | 18 |
| Caps7: | 20 |
| Caps8: | 74 |
| Goals2: | 11 |
| Goals3: | 15 |
| Goals4: | 0 |
| Goals5: | 8 |
| Goals6: | 2 |
| Goals7: | ? |
| Goals8: | 6 |
Mario Castellazzi (9 November 1935 – 1 October 2018) was an Italian professional footballer.
He played for 3 seasons (57 games, 8 goals) in the Serie A for A.S. Roma and Calcio Catania.