Petritsi () is a former municipality in the Serres regional unit, Greece. Since the 2011 local government reform it is part of the municipality Sintiki, of which it is a municipal unit, with a population of 3,900 (2021). The municipal unit has an area of 253.075 km<sup>2</sup>. The seat of the municipality was in Neo Petritsi.
The settlement is served by Petritsi railway station on the Thessaloniki-Alexandroupoli line, with daily services to Thessaloniki and Alexandroupolis.