Namdaecheon (남대천, 南大川) is a river in Cheolwon county, Gangwon-do. It is 39.70 km long, with a total surface area of 333.60㎢. It starts in Gimhwa county on the 642-metre high peak of Suribong (수리봉), and flows north into the Hantan River (한탄강).

There is also a river of the same name in the city of Gangneung: see Namdaecheon (Gangneung).