Sumner is a city in Bremer County, Iowa, United States. The city is located along the county's eastern border, between Bremer and Fayette counties. The population was 2,028 at the 2010 census. The Bremer County portion of Sumner is part of the Waterloo–Cedar Falls Metropolitan Statistical Area.
The town was established in 1870, and incorporated in 1894. The community is named after American political leader Charles Sumner.
Sumner is home to Life Line Emergency Vehicles, a major manufacturer of ambulances.