Bancroft is a city in the Gem Valley of Caribou County, Idaho, United States. The population was 377 at the 2010 census.
The community was named after William H. Bancroft, a railroad official.
Bancroft is located at 42°43′10″N 111°53′10″W (42.719440, -111.886194), in the Portneuf Valley. It is a railroad town and lies on the historic route of old U.S. Highway 30. The elevation is 5,420 feet (1,650 m).
According to the United States Census Bureau, the city has a total area of 0.65 square miles (1.68 km2), all of it land.
As of the census of 2010, there were 377 people, 138 households, and 104 families living in the city. The population density was 580.0 inhabitants per square mile (223.9/km2). There were 163 housing units at an average density of 250.8 per square mile (96.8/km2). The racial makeup of the city was 96.0% White, 0.3% Native American, 0.8% from other races, and 2.9% from two or more races. Hispanic or Latino of any race were 3.2% of the population.