Walter Hahn, better known by his ring name Gunther, is an Austrian professional wrestler signed to WWE, where he performs on the Raw brand. He signed with WWE in 2018, became the longest-reigning NXT United Kingdom Championship holder at 870 days, later moved to the main roster, set a record with a 666-day WWE Intercontinental Championship reign, won the World Heavyweight Championship twice, became the 24th King of the Ring, and defeated Goldberg, John Cena, and AJ Styles in their retirement matches.

Before joining WWE, Hahn made his professional wrestling debut in 2005 with IWA Switzerland and gained prominence in Europe under the names Big Van Walter, Big Daddy Walter, and Walter, most notably in Westside Xtreme Wrestling (wXw), where he was a three-time Unified World Wrestling Champion, four-time World Tag Team Champion, and head trainer of the wXw Wrestling Academy from 2015 to 2020. He also competed internationally for promotions including Big Japan Pro Wrestling (BJW), Pro Wrestling ZERO1, PROGRESS Wrestling, Pro Wrestling Guerrilla (PWG), and Over The Top Wrestling (OTT), holding multiple world titles across the independent circuit.