| Type: | Cardinal |
| Honorific Prefix: | His Eminence |
| Pietro Giannelli | |
| Cardinal-Priest of Sant'Agnese fuori le mura | |
| Church: | Roman Catholic Church |
| Appointed: | 31 March 1875 |
| Term End: | 5 November 1881 |
| Predecessor: | Lorenzo Barili |
| Successor: | Charles-Martial Allemand-Lavigerie |
| Ordination: | 3 October 1830 |
| Ordained By: | Niccola Mazzoni |
| Consecration: | 6 June 1858 |
| Consecrated By: | Costantino Patrizi Naro |
| Cardinal: | 15 March 1875 |
| Created Cardinal By: | Pope Pius IX |
| Rank: | Cardinal-Priest |
| Birth Name: | Pietro Giannelli |
| Birth Date: | 1807 8, df=yes |
| Birth Place: | Terni, Papal States |
| Death Place: | Rome, Kingdom of Italy |
| Parents: | Pietro Giannelli Olimpia Petroni |
| Previous Post: | Titular Archbishop of Sardes (1858-75) Secretary for Seminaries of the Congregation of the Council (1861-68) Secretary of the Congregation of the Council (1868-75) |
Pietro Giannelli (11 August 1807 – 5 November 1881) was an Italian prelate who was elevated to the cardinalate in 1875.