St. Charles is a city in southern Bear Lake County, Idaho, United States, that is located near the northwestern shore of Bear Lake. Its population was 131 at the 2010 census, down from 156 in 2000.

Bear Lake County is a county in the U.S. state of Idaho. As of the 2020 United States Census the county had a population of 6,372. The county seat is Paris, and Montpelier is the largest city.