Untereggen is a municipality in the Wahlkreis (constituency) of Rorschach in the canton of St. Gallen in Switzerland.

Of the rest of the land, 5.5% is settled (buildings or roads) and the remainder (1.4%) is non-productive (rivers or lakes).

[3] The blazon of the municipal coat of arms is Argent a Crow Sable statant on Coupeaux Gules.

Of the foreign population, (as of 2000[update]), 11 are from Germany, 20 are from Italy, 2 are from ex-Yugoslavia, 2 are from Austria, and 5 are from another country.

[7] The age distribution, as of 2000[update], in Untereggen is; 171 children or 19.1% of the population are between 0 and 9 years old and 131 teenagers or 14.6% are between 10 and 19.

[10] From the 2000 census[update], 580 or 64.7% are Roman Catholic, while 257 or 28.7% belonged to the Swiss Reformed Church.

[7] The Sulzberg in Untereggen is designated as part of the Inventory of Swiss Heritage Sites.