Pietro Nelli (1672 – after 1730) was an Italian painter of the late-Baroque period.
He was born in Massa, where he had been a pupil of Giovanni Maria Morandi in Rome. He was known for his portraits including those of Cardinal Lodovico Pico (engraved by Frey); Andrea Giuseppe Rossi (engraved by Niccolo Billy); and Bishop Giovanni Francesco Tenderini (engraved by Giovanni Battista Rossi).