Seyyed Taj ol Din () is a village in Qarah Su Rural District of the Central District in Khoy County, West Azerbaijan province, Iran.
At the time of the 2006 National Census, the village's population was 2,490 in 482 households. The following census in 2011 counted 2,575 people in 669 households. The 2016 census measured the population of the village as 2,612 people in 736 households. It was the most populous village in its rural district.