Early career Starting his career in 2015, Jung compiled a 11–2 record fighting for various East Asian regional promotions, with his most memorable accomplishment being winning the HEAT Light Heavyweight Championship via TKO against Yuto Nakajima.
Ultimate Fighting Championship Jung made his UFC debut against fellow newcomer
Khadis Ibragimov on August 31, 2019, at
UFC Fight Night 157. He won the fight via standing guillotine in the third round. Jung faced
Mike Rodríguez on December 21, 2019, at
UFC Fight Night 165. He won the fight via knockout in the first round. Da Un Jung was scheduled to face
Ed Herman on May 2, 2020, at
UFC Fight Night: Hermansson vs. Weidman. However, on April 9,
Dana White, the president of UFC announced that the event was postponed to a future date. The bout with Herman was rescheduled for August 1, 2020, at
UFC Fight Night 175. However, Jung was removed from the bout on July 23 due to alleged travel restrictions related to the COVID-19 pandemic. Jung faced
Sam Alvey on October 24, 2020, at
UFC 254. After a back and forth battle, the fight was declared a draw. 17 out of 21 media outlets scored the bout for Alvey. As the first bout of his new contract, Jung was scheduled to face
Shamil Gamzatov on April 10, 2021, at
UFC on ABC 2. However, Gamzatov was removed from the bout on March 24 due to alleged
Visa issues and replaced by
William Knight. Jung won the bout via unanimous decision. Jung was scheduled to face
Kennedy Nzechukwu on October 16, 2021, at
UFC Fight Night 195. However, the bout was postponed to
UFC Fight Night 197 on November 13, 2021, for unknown reasons. Jung won the bout via knockout in round one. Jung faced
Dustin Jacoby on July 16, 2022, at
UFC on ABC 3. He lost the fight via knockout in the first round. Jung faced
Devin Clark on February 4, 2023, at
UFC Fight Night 218. He lost the fight via unanimous decision. Jung faced
Carlos Ulberg on September 10, 2023, at
UFC 293. He lost the fight in round three via rear-naked choke. Jung faced Oumar Sy on September 28, 2024 at
UFC Fight Night 243. He lost the fight by unanimous decision. On October 8, 2024, following his loss, it was reported that Jung was removed from the UFC roster.
Post UFC On December 21, 2024, it was reported that Jung had signed with Global Fight League. Jung was scheduled to face
Ronny Markes on May 25, 2025 at GFL 2. However, all GFL events were cancelled indefinitely. ==Championships and accomplishments==