Alt St. Johann is a village in the Toggenburg region, since 2010 part of the municipality Wildhaus-Alt St.Johann in the canton of St. Gallen in Switzerland (the former municipalities of Alt St. Johann and Wildhaus merged on 1 January 2010).

Alt St. Johann is historically the site of a monastery dedicated to Saint John the Baptist, first mentioned in 1152.

From 1414, the castle passed to the counts of Toggenburg, and after their extinction to St. Johann abbey.

Of the rest of the land, 2.1% is settled (buildings or roads) and the remainder (11.8%) is non-productive (rivers or lakes).

Of the foreign population, (as of 2000[update]), 19 are from Germany, 3 are from Italy, 91 are from ex-Yugoslavia, 8 are from Austria, and 37 are from another country.

[5] The age distribution, as of 2000[update], in Alt St. Johann is; 159 children or 10.9% of the population are between 0 and 9 years old and 252 teenagers or 17.3% are between 10 and 19.

[2] Out of the total population in Alt St. Johann, as of 2000[update], the highest education level completed by 374 people (25.7% of the population) was Primary, while 502 (34.5%) have completed their secondary education, 118 (8.1%) have attended a Tertiary school, and 74 (5.1%) are not in school.

[5] The historical population is given in the following table:[1] The paleolithic cave, Wildenmannlisloch is listed as a Swiss heritage site of national significance.

[9] From the 2000 census[update], 681 or 46.9% are Roman Catholic, while 531 or 36.5% belonged to the Swiss Reformed Church.