Pyotr Timofeyevich Mstislavets (Timofeyev) (Пётр Тимофеевич Мстиславец (Тимофеев) in Russian) (? - ?) was a Russian printer and Ivan Fedorov's associate.

Historians believe that Pyotr Mstislavets was born in a Belarusian town of Mstislavl . Together with Ivan Fedorov, he printed the first Russian dated printed book Apostole (Апостол) on March 1, 1564 in Moscow. In 1565 Pyotr Mstislavets printed two editions of the Breviary (Часовник). Soon he and Ivan Fedorov had to leave Moscow. They opened a new print shop in Zabludovo (Lithuania) on the premises of the estate of hetman Jeremi Chodkiewicz . Here Mstislavets and Fedorov printed The Gospel (Учительное евангелие) in 1568-1569. In the summer of 1569 Mstislavets left for Vilnius and soon opened a print shop, equipped and financed by merchants Mamonichs. Here he printed the so-called Quadruple Gospel (Четвероевангелие) in 1574-1575, which contained four full-page engravings of evangelists. In January of 1576 Mstislavets finished printing the Psalter (Псалтырь) with a frontispiece engraved in wood (Tsar David, or Царь Давид), multiple illuminations and decorated capital letters. In 1576 Mstislavets severed his relations with the Mamonichs. The court mandated him to return all of his printed books to the merchants and allowed him to keep his typographical equipment. Historians believe that after this incident Mstislavets continued his printing activities in Ostrog, Ukraine.