Rat Niyom (Thai: ราษฎร์นิยม, pronounced [râːt ní(ʔ).jōm]) is one of the seven subdistricts (tambon) of Sai Noi District, in Nonthaburi Province, Thailand. The subdistrict is bounded by (clockwise from north) , , , Lahan, Khlong Khwang, Khun Si and Sai Yai subdistricts. In 2020 it had a total population of 6,759 people.