Siyah Nab () is a village in Mehranrud-e Markazi Rural District of the Central District in Bostanabad County, East Azerbaijan province, Iran.
At the time of the 2006 National Census, the village's population was 843 in 184 households. The following census in 2011 counted 826 people in 200 households. The 2016 census measured the population of the village as 826 people in 223 households.