Pietro Gagliardi (9 August 1809 – 19 September 1890) was an Italian painter and architect, who decorated many churches and palaces in Rome and throughout Italy.

He worked primarily in Rome, and his studio was located in Palazzo Giustiniani in Piazza San Luigi dei Francesi.

By the 1840s, he had established himself as a preeminent painter of sacred art and was active in and around Rome, especially in Tarquinia, where he worked with his nephews Francesco and Giovanni.

In 1857, he became a member of the Pontifical Academy of Fine Arts and Letters of the Virtuosi al Pantheon, and served as president and regent several times beginning in 1888.

Gagliardi died in Frascati on 19 September 1890 and was buried alongside his family and wife, Vittoria Roscioli, in the Chapel of San Giuseppe in the Church of Sant'Agostino in Rome, which he restored and painted.