Rud Ab District (Persian: بخش رودآب) is a district (bakhsh) in Sabzevar County, Razavi Khorasan Province, Iran. At the 2006 census, its population was 14,611, in 4,163 families. The District has one city: Rud Ab. The District has three rural districts (dehestan): Frughan Rural District, Khavashod Rural District, and Kuh Hamayi Rural District.