Namdaecheon (남대천, 南大川) is a river in the city of Gangneung that flows east into the East Sea / Sea of Japan. It is 32.86 km in length, with a total surface area of 258.65㎢. It starts from Daehwashil mountain.

There is also another river with the same name in the same province: see Namdaecheon (Cheolwon).