Rudiyan (), formerly known as Ruyan (, also Romanized as Rūyān) is a city in the Central District of Shahrud County, Semnan province, Iran.

At the 2006 census, its population was 3,295 in 871 households, when it was a village named Ruyan in Howmeh Rural District. The following census in 2011 counted 3,266 people in 1,039 households. The latest census in 2016 showed a population of 3,770 people in 1,228 households, by which time the village had risen to the status of city and its name had changed to Rudiyan.

References 

Shahrud County

Cities in Semnan Province

Populated places in Shahrud County