Waterloo is a city in Jefferson County, Wisconsin, United States.

29.2% of all households were made up of individuals, and 23.1% had someone living alone who was 65 years of age or older.

The city is the headquarters for Trek Bicycle Corporation and Van Holten Pickles.

Waterloo is a part of the Milwaukee television market with Madison based stations also available over the air and on cable.

Waterloo is served by radio stations from the Milwaukee, Madison and Janesville markets.