Masiri (Persian: مصيرئ) is a city in the Central District of Rostam County, Fars province, Iran, serving as capital of both the county and the district. It is also the administrative center for Rostam-e Yek Rural District.

At the 2006 National Census, its population was 5,365 in 1,178 households, when it was in the former Rostam District of Mamasani County. The following census in 2011 counted 5,830 people in 1,488 households, by which time the district had been separated from the county in the establishment of Rostam County. The latest census in 2016 showed a population of 9,031 people in 2,592 households.