Allendorf is an unincorporated community in Osceola County, Iowa, United States.

It is located on Highway 59, five miles east of Sibley, at 43.413270N, -95.64318W,[1] adjacent to the Johnson Wilderness Area.

Allendorf was founded in 1895, possibly named after a town named Allendorf in Germany; the town was originally named Oliver.

[2] Allendorf's population was 13 in 1902,[3] and 35 in 1925.

[4] The population was 60 in 1940.