Jeong Yun-o (Korean: 정윤오; born Jeong Jae-hyun (Korean: 정재현); February 14, 1997), better known by his stage name Jaehyun, is a South Korean singer and actor. He is a member of the South Korean boy group NCT and its sub-units NCT U and NCT 127, debuting in April 2016 as a member of the rotational unit NCT U and as a member of Seoul-based fixed unit NCT 127 in July 2016.

Jaehyun hosted the television program Inkigayo from October 2019 to February 2021. As an actor, he made his debut with a leading role in the college-romance television series Dear. M (2022).

Jaehyun was born on February 14, 1997, in Seocho District, Seoul, South Korea. Although he was born Jeong Jae-hyun (정재현), he later legally changed his name to Jeong Yun-o (정윤오). Between the ages of 5 and 10, Jaehyun lived and studied in Connecticut in the United States and went by the English name Jay Jeong. As a result, he is fluent in both English and Korean. Jaehyun became interested in music at a young age due to his parents' influence, and learned how to play the guitar and the piano, and later began singing during middle school. His grandmother, a retired professional dancer, was also his guide during dance training. He attended Shindong Middle School and Apgujeong High School. He transferred to the School of Performing Arts Seoul in his second year of high school and graduated in 2016. He used to be a student council president.

2012–2016: Pre-debut

Jaehyun was cast by SM Entertainment in 2012, discovered by street scouts in front of his school. He auditioned with a performance of "Mama" by Exo. On December 9, 2013, he was introduced as a member of the pre-debut trainee team SM Rookies. In 2014, he participated with fellow NCT members on the show Exo 90:2014, where they performed songs from the 1990s. From January 21 to July 1, 2015, he and groupmate Doyoung were MCs on Show Champion. In July 2015, he and groupmate Ten both competed in Hope Basketball All-Star. In December 2015, Jaehyun performed "A Whole New World" on Disney Channel Korea's The Mickey Mouse Club.

2016-2018: Debut with NCT

In April 2016, Jaehyun officially debuted as a member of the first NCT's sub-unit, NCT U, with the singles "The 7th Sense" and "Without You". On July 10, he made his debut as a member of NCT 127 with their first EP, NCT#127. In March 2017, Jaehyun joined the radio show NCT Night Night as a DJ alongside fellow member Johnny. In November 2017, Jaehyun and Dear released the song "Try Again" for the project SM Station. In December, he was featured in the music video for Wendy and Baek A-yeon's "The Little Match Girl". In January 2018, Jaehyun released the single "Timeless" alongside a new NCT U lineup as part of the SM Station project.

2019–present: Solo endeavors and acting debut

In October 2019, Jaehyun became one of three hosts for the South Korean music program Inkigayo alongside Minhyuk and Naeun, hosting the show every Sunday. On September 4, 2020, it was confirmed that Jaehyun would make his acting debut in the KBS2 drama Dear. M, which was to be released in 2021, in the role of Cha Min-ho, a second year student in the Computer Science Department at Seoyeon University. The drama was postponed indefinitely for airing after the lead actress, Park Hye-su, was accused of school bullying. After nearly two years of delay, the first six episodes of Dear. M was released globally on June 29, 2022 through the streaming service Viki. Its following episodes were released on July 6, 2022.

On November 2, 2021, Jaehyun was confirmed to star in a KakaoTV web series, a remake of the 2001 South Korean film Bungee Jumping of Their Own, playing the leading role of Im Hyun-bin. On December 9 of the same year, during pre-production, KakaoTV announced the cancellation of the project due to concerns with the LGBT plot from the original film's screenwriter. On August 18, Jaehyun released his first single "Forever Only" as part of NCT Lab. "Forever Only" is described as an R&B song featuring lyrics written by Jaehyun.

Ambassadorship

Following various successful collaborations with Prada, the brand selected Jaehyun as an ambassador in 2022, citing his influence and unique fashion style as a reason.

Everyone's life is different. There are those who think music is just noise and trash, there are also those who think otherwise. Of course I'm a person with the second option. Myself understand that other people's tastes and perspectives are different, but respecting others as long as they don't go astray is that okay? Just to make small talk, I used to dream of becoming a great musician that everyone likes. Staring at me with sparkling eyes, and full of admiration. The universe is like saying, yes, I will obey. Standing here alone, singing a song that I composed myself 2 years ago, it feels as much as I like that song. Deep voice, crazy expressions I made solely to drive fans crazy.

The moon──── deeply creative and intuitive, and many people find you mysterious. You can be manipulative and have a dark side that you're good at hiding, and maybe have a few skeletons in your closet. That said, there's a distinct dreamlike quality about you ── some might even say psychic.

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