Sian (, also Romanized as Sīān, Seyān, and Sīyān; also known as Shiān, Siūni, and Sīyūnī) is a village in, and the capital of, Rudasht Rural District of Ezhiyeh District, Harand County, Isfahan province, Iran.
At the 2006 National Census, its population was 581 in 151 households, when it was in the former Jolgeh District of Isfahan County. The following census in 2011 counted 563 people in 161 households. The latest census in 2016 showed a population of 556 people in 167 households. It was the largest village in its rural district.
The district was separated from Isfahan County in 2021 to become Harand County. The new county was divided into two districts, with two rural districts and one city each, and the city of Harand was chosen as its capital.