Nyūzen (入善町, Nyūzen-machi) is a town in Shimoniikawa District, Toyama Prefecture, Japan.

With the Sea of Japan to the north, and Kurobe River to the west, Nyūzen is in the center of an alluvial fan.

Of special interest is a flat area near the coast the name of which translates to: The Japanese Swamp Cedars of Sugisawa (杉沢の沢スギ, Sugisawa no Sawasugi) where a large volume of flowing spring water has created a rare ecosystem that is protected as a natural monument.

The town has a humid subtropical climate (Köppen Cfa) characterized by hot summers and cold winters with heavy snowfall.

The area was organised as part of Shimoniikawa District, Toyama after the Meiji restoration.