Nashua is a city in Chickasaw and only partly in Floyd counties in the U.S. state of Iowa. As of the 2010 census, the city's population was 1,663 an increase of 45, or 2.8%, 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.