Nashua is a city in Chickasaw and only partly in Floyd counties in the U.S. state of Iowa. As of the 2020 census, the city's population was 1,551 a decrease of 67, or 4.1%, from 1,618 reported at the 2000 census. The famed Little Brown Church featured in the song "The Church in the Wildwood" is located in Nashua.