His nickname, The Korean Zombie, comes from his perceived zombie-like ability to continue to move forward and fight aggressively, even after taking heavy blows.

[6] Born in Pohang, South Korea in 1987, Jung moved to Namyangju, a satellite city of Seoul when he was in his mid-teens.

[8] In June 2007, he won a Sambo tournament arranged by the Korean Sambo Association, and in December of the same year, he won the Lightweight division of the Pancrase Korea Neo-Blood Tournament after defeating fellow South Koreans Yoo In Seok and Lee Hyung Geol.

[8] Jung was also a participant in a show called Street Fighter in 2007 which aired on South Korean cable television.

Jung made his professional debut in June 2007 and in December the same year, he won a Lightweight Tournament arranged by Pancrase Korea.

He then entered the 2009 Sengoku Featherweight Grand Prix where he won his first-round fight but was eliminated from the tournament by the eventual winner Masanori Kanehara.

[11] In his second-round fight at Sengoku 8 on May 2, 2009, he lost via unanimous decision to Masanori Kanehara officially eliminating him from the tournament.

On June 7, 2009, it was announced Jung would face American Matt Jaggers at Sengoku 9 in a reserve bout for the tournament with the winner stepping in as a replacement should some of the remaining fighters be unable to continue.

[13] Jung ended up winning the fight by triangle choke submission at 1:25 of the second round, but was not required to step in as a replacement.

Many MMA publications and fans (including many in the Sacramento home crowd) opposed the decision, which has led again to questions about the accuracy of the fight judging.

[22] A rematch with Garcia was scheduled for March 26, 2011, at UFC Fight Night 24, after Jung stepped in to replace an injured Nam Phan.

[24] In his post-fight interview, Jung stated he learned the move by watching Eddie Bravo videos on YouTube.

Jung won the bout via KO at seven seconds of the first round, which tied a UFC record for the fastest knockout at the time.

[26] The victory also earned Jung much praise in his native South Korea, appearing on news broadcasts on the country's major national television channels (such as KBS).

[36] Jung announced in mid-October 2014 his intention to begin his stint for mandatory military service in his home country of South Korea.

While Jung did not comment about the future upon his completion, his manager indicated that he would return to mixed martial arts at the end of the two years.

[52] However, Ortega pulled out of the fight in early December citing a knee injury[53] and he was replaced by Frankie Edgar.

[63] For the last time in his MMA career, Jung faced Max Holloway on August 26, 2023 at UFC Fight Night 225.