Niederhelfenschwil is a municipality in the Wahlkreis (constituency) of Wil in the canton of St. Gallen in Switzerland.

Of the rest of the land, 8.4% is settled (buildings or roads) and the remainder (0.6%) is non-productive (rivers or lakes).

It consists of the villages of Niederhelfenschwil, Lenggenwil and Schloss Zuckenriet as well as the hamlets of Enkhüseren, Dietenwil and Dägetschwil.

The blazon of the municipal coat of arms is Azure between a Pall Or letters N, L and Z[5] Niederhelfenschwil has a population (as of 31 December 2020) of 3,181.

Of the foreign population, (as of 2000[update]), 34 are from Germany, 16 are from Italy, 50 are from ex-Yugoslavia, 9 are from Austria, 5 are from Turkey, and 44 are from another country.

[8] The age distribution, as of 2000[update], in Niederhelfenschwil is; 475 children or 18.3% of the population are between 0 and 9 years old and 406 teenagers or 15.6% are between 10 and 19.

[8] The historical population is given in the following table:[3] The Catholic parish church of St. John the Baptist and Zuckenriet Castle are listed as Swiss heritage sites of national significance.

[12] From the 2000 census[update], 1,798 or 69.2% are Roman Catholic, while 523 or 20.1% belonged to the Swiss Reformed Church.