Mellen is a city in Ashland County, Wisconsin, United States. The population was 698 at the 2020 census.

Mellen has a mayor-council form of government.

According to the Mellen Weekly-Record; Vol.123 No. 29; Wednesday, July 20, 2022, Mayor Joseph A. Barabe, resigned effective at noon, on July 15, 2022. No further explanation was given. Nathaniel Delegan, President of the Mellen City Council, served as Acting Mayor until the election of a new Mayor on April 4, 2023.

The Mellen City Council is considering changing the form of government. Mellen currently has a Mayor-Council form of government. The city council is considering three options. The first option is to remain with the Mayor-Council form of government. The second option is to establish the position of City Administrator, who operates under the Mayor. The third option is to abolish the Office of Mayor and establish a Manager-Council type of government.

In the Wisconsin State Legislature, Mellen is located in the 74th Assembly District, and the 25th Senate District, represented by Assembly Representative Chanz Green and State Senator Romaine Quinn

In the United States House of Representatives, Mellen is served by Tom Tiffany, of Wisconsin's 7th congressional district.

Mellen is located at 46°19′27″N 90°39′33″W / 46.32417°N 90.65917°W / 46.32417; -90.65917 (46.324288, -90.659295), along the Bad River.

According to the United States Census Bureau, the city has a total area of 1.87 square miles (4.84 km²), all land.