Brillion is a city in Calumet County in the U.S. state of Wisconsin. The population was 3,538 as of 2024. The city is located within the Town …Brillion is a city in Calumet County in the U.S. state of Wisconsin. The population was 3,538 as of 2024. The city is located within the Town of Brillion, though it is politically independent. Brillion is named after the town of Brilon, in Germany.