Butler County is a county located in the U.S. state of Iowa. As of the 2020 census, the population was 14,334. Its county seat is Allison. The county was organized in 1854 and named for General William O. Butler.

William Orlando Butler was a U.S. political figure and U.S. Army major general from Kentucky. He served as a Democratic congressman from Kentucky from 1839 to 1843, and was the Democratic vice-presidential nominee under Lewis Cass in 1848.