Glenn Jacobs, better known as Kane, ran as the Republican candidate in the state’s third most populous county, defeating Democrat Linda Haney by 31,739 votes to 16,611.
The 51-year-old campaigned on promises of tax cuts as well as improvements to education and infrastructure.
Mr Jacobs has won a string of professional wrestling titles during a decades-long career, including the WWF Championship, WWE World Heavyweight Championship and ECW Championship.
The WWE congratulated Mr Jacobs in a statement, writing: “Kane has been elected Mayor of Knox County, Tenn., tonight, capping a path to office that began over a year ago for the former WWE Champion.”
The wrestling giant told WBIR he was "very happy" to be elected and thanked his team, volunteers and "the people of Knox County".
Fan favourite Kane traditionally wrestles in a red mask, leading to the nickname “the big red machine”.
Mr Jacobs will assume office in Knox County on September 1.
