Petru I Muşat was Voivode (prince) of Moldavia from 1375 to 1391, the son of Costea Muşat, the first ruler from the dynastic House of Bogdan. During his reign, he maintained good relationships with his neighbours, especially Poland.
On September 27, 1387, at Lwów he paid homage to the Polish king Władysław II Jagiełło, making Moldavia a Polish fief (which it remained until 1497). In 1388, he received Pokuttya as a pawn for 3,000 silver rubles he lent to the Polish king. Petru also acted as an intermediary in the negotiations between the Wallachia voivode Mircea cel Bătrân and the Polish king that resulted in the treaties signed by the two parts in 1389 and 1390. The first Russian-Moldavian diplomatic contacts also date from his reign.
Petru I founded the fortress and the monastery in Neamţ, and built the Holy Trinity Church in Siret. He also fixed the see of Moldova at Suceava and maintained Bishop Iosif at Cetatea Albă, contrary to the wishes expressed by the Patriarchate of Constantinople, resulting in his excomunication.
During his reign, a number of important coins were minted; the ones attributed to him, known so far, are: groschen and far more rare half-groschen made of silver. Their design became the standard for coins minted by later Moldavian rulers.
Obverse: Aurochs head, frontal view, a star between the horns, a rose on the right, a crescent on the left. In some cases, the rose is at left and the crescent at right. Sometimes, the aurochs holds a fleur de lys in its mouth. The legend is in Latin: SIMPETRI WOIWOD.
Reverse: Coat of arms, a shield with three or four bars in the right half, and in the left half a variable number of fleurs de lys (seven to one). The legend is SIMOLDAVIENSIS.