Yoonchan Kwak (곽윤찬, in Korean order Kwak Yoon-chan, sometimes romanized Gwak Yun-chan) is a Seoul-born jazz pianist, composer and university professor. He is best known in Korea as the pianist whom the press calls the first Korean artist signed to Blue Note: his third album, Noomas (2005), and his fourth, Yellowhale (2007), came out on that label according to his Kyobo Book Centre biography, and Korean newspapers have repeated the "first Korean" description since 2006. His fifth album, 49 (Sony Music, 2013), was a turn to fusion with the singer Brian McKnight, the guitarist Paul Jackson Jr., the saxophonist Eric Marienthal and the drummer Vinnie Colaiuta. He appears as Yoonchan Kwak on his album covers, streaming pages and YouTube channel, and as Kwak Yoon Chan in the Discogs entry for 49.

He was born in Seoul in 1968, and a Kyobo Book Centre biography gives the date as September 27. In a 2003 interview he said his father was a jazz enthusiast whose records, above all swing played by the accordionist Art Van Damme, he listened to for years, and that he began classical piano lessons at seven while staying curious about jazz. He chose composition at Chugye University for the Arts because it was the closest course to jazz, and practised in secret because his parents objected. While still enrolled he left for Tokyo, because, he said, learning jazz in Korea was close to impossible at the time, while Japan offered concerts, scores and information and made self-teaching possible; he graduated from the Muse Music Academy there (in 1989, by his Kyobo biography). He then studied at the Berklee College of Music in Boston. Kyobo dates his Berklee graduation to 1993, while newspapers say he came home in 1996 after giving a trio concert at the Berklee Performance Center. He told OhmyNews that Japan gave him information and theory and that America taught him the depth of jazz feel, the rhythm and swing felt in the body.

Back in Seoul he formed a contemporary jazz group called Cool and worked alongside the saxophonist Lee Jung-sik, the trumpeter Juhan Lee and the bassist Jeon Seong Sik, according to OhmyNews. By April 1999 the Seoul Shinmun listed him as a piano instructor at the Seoul Jazz Academy, and he was lecturing at Dongduk Women's University by 2003. His first recorded work in Korea was as a sideman: he plays piano on tracks 1 and 3 to 10 and keyboards on tracks 1 and 11 of Lee Jung-sik's Hwadu: The Korean Jazz Standards Vol. 1 (BMG Korea, April 1999), and arranged "사노라면" (track 7). He told the Kyunghyang Shinmun in 2006 that he held back from releasing records under his own name on purpose, because a leader album is a declaration that one is a professional.

His first album, Sunny Days, came out in September 2001 on Universal's EmArcy label, which Korean press describes as a first for a Korean musician. The bassist John Clayton and the drummer Jeff Hamilton are credited on the tracks his own YouTube channel posts. He described it to Kyunghyang as acoustic and recorded the old way, with a warm, analog feel. Daisy followed in 2003. His channel credits John Clayton on bass and Gregory Hutchinson on drums for the tracks it posts, while Korean press names Hamilton, Hutchinson, the alto saxophonist Jeff Clayton and the guitarist Larry Koonse among the album's players. OhmyNews reported that on February 23, 2003 he marked its release with a concert at the Seoul Arts Center Concert Hall alongside Jeff Clayton, Koonse, the bassist Jack Mathew and the drummer Roland Bruner Jr. In 2006 the artist Lee Seul-gi included two pieces titled "Green Tees" and "Grace", credited to Kwak as composer and pianist with Heo Jin-ho on bass and Oh Jong-dae on drums, on her album In the Green Café Vol. 2; both titles are also on Daisy.

Noomas (2005) is the album that earned the headlines. Kyunghyang reported in May 2006 that it had been issued in the United States on Blue Note and that his first two albums had been re-released on the label as well, making him the first Korean on Blue Note. He told the paper he chose a trio format for this third album to appeal to an international audience, and his channel credits John Patitucci on bass and Nasheet Waits on drums. The record includes "Beethovenesque", his jazz arrangement of Beethoven's Piano Sonata No. 8, the "Pathétique", with a closing section he wrote himself, beside standards and originals such as "Noomas" and "Being Not Doing". Yellowhale (2007) was recorded in New York with the bassist Drew Gress and Waits, and a Seoul Arts Center concert on February 13, 2008 presented it with Lee Jung-sik and the Clazziquai singer Horan as guests. In a 2022 interview he said he made four regular albums on Blue Note and that carrying the label's name helped him recruit musicians such as Brian McKnight. Jazz People magazine's readers' poll also ranked him first among pianists.

49 was released on April 9, 2013, with a press conference at Sony Music Korea the day before. In Tenasia's report he said fusion was a music he had wanted to play since childhood and that his earlier leader albums had shown the essence of bebop. Brian McKnight agreed to take part after reading the chart he sent, and the song "Ever Forever Whenever" was McKnight's first recording of a song written by a Korean. The pianist said recruiting Paul Jackson Jr., Eric Marienthal and Vinnie Colaiuta was close to impossible and that he had pursued Jackson for three years. The album was recorded in the United States, Jackson recording in his own studio, and the pianist mixed it himself. The title track and "Opening Bell", which grew from a ringtone he wrote for his wife's phone, lead its nine tracks; the bassist Alex Al and the percussionist Lenny Castro are credited on his channel, and the singer Na Ul of Brown Eyed Soul designed the cover. He said the musicians on the record had proposed a live album and that McKnight's side had talked of touring together, but that he would have to make the decision himself.

A second strand of his work is explicitly Christian. He has said he joined a church at five, and he describes jazz as the "New Testament" to classical music's "Old Testament". The i am Melody albums, of which he described three by 2017, bring him together with Korean pop and gospel singers including Na Ul, Park Ki-young, Jang Hee-young, Tim, Lee Ha-nui, Seo Young-eun, Jang Yoon-ju and Lisa, and a book of the same name carries the subtitle "Kwak Yoon-chan's Happy Jazz Story That Comforts the World". Tenasia adds that he has made gospel albums with Na Ul and Kim Bum-soo, and he released a piano-only set of eight hymns, i am Melody Piano Version, in 2020. La (November 2016), his sixth album, was his first solo piano album, built on lyrical ballads with a hymn as its last track, and in December 2017 he said the next one would be a one-man-band record in which he handled everything except vocals.

Recent years have brought a steady stream of releases, most of them on the Blueshrimp label: OLIVET (January 2022, issued by Keiser), which Gangwon Domin Ilbo calls his ninth regular album and which was made in online collaboration with musicians abroad; After You've Gone (January 2024); the single META MAX episode 1 (January 2024); the 17-track When You Study Upon a Star (February 2025); The First Foundation (September 2025); and a hymn single in April 2026. Alongside the leader work he has been a professor of practical music at Korea Nazarene University (나사렛대학교) and head of its department by 2012, and on April 16, 2022 he played the Daegwallyeong Music Festival's "All the Pianos of the World" series, where he performed his jazz arrangement of Beethoven's Sonata No. 8. In that interview he recalled meeting the classical pianist Son Yeol-eum, who came to him in 2011 to learn about jazz, and introducing her to free improvisation.

He is a mainstream pianist who prefers the bebop idiom. Kyunghyang quoted him in 2006 saying that people liken him to Bill Evans, that he does not much like Evans, that many players had influenced him, and that bebop felt most natural to him, from fast swing to slow ballads. The same article describes a disciplined routine: he gets up early, sits down at the piano and tries to rest in the evening. In 2022 he told Gangwon Domin Ilbo that apart from the theme he improvises everything in "Beethovenesque", and that even the length of a performance depends on the mood of the room; the paper describes his playing as accenting the weak beats, with delicacy and freedom.

His records move between settings. Sunny Days, Daisy, Noomas and Yellowhale are acoustic, built on standards ("Stella by Starlight", "Autumn Leaves", "Round Midnight", "Someday My Prince Will Come") and his own pieces. 49 is fusion with a pop vocalist. La is solo piano, and the hymn albums fold Christian songs into jazz piano. He says faith and jazz belong together, in that music is an ordered design rather than an accident, and that jazz, unlike the written classical tradition, gives room to improvise.