| Gianni de Magistris | |
| Nationality: |  Italy |
| Birth Date: | 1950 12, df=yes |
| Birth Place: | Florence, Italy |
| Height: | 1.85m (06.07feet) |
| Weight: | 82kg (181lb) |
| Sport: | Water polo |
| Club: | Rari Nantes Florentia |
| Show-Medals: | yes |
Gianni De Magistris (born 3 December 1950 in Florence, Italy) is a retired Italian water polo player. He was part of Italian teams that won the world title in 1978, a silver medal at the 1976 Olympics, and two bronze medals, at the 1975 world and 1977 European championships.
Magistris played in five consecutive Summer Olympics for Italy from 1968 to 1984 (at the 1976 games, younger brother Riccardo was among his teammates). He is the third athlete to compete in water polo at five Olympics, after Briton Paul Radmilovic and Hungarian Dezső Gyarmati. He is among the first ten Italians to compete at five Olympics. He is also a leading scorer in Olympic water polo history, with 59 goals.