Jeon Seong Sik (전성식) is a South Korean double bassist who has worked in the Seoul jazz scene since at least the mid-1990s. He has led three records of his own, a film-score quartet in 2000, the trio album Twilight with the Swedish guitarist Ulf Wakenius in 2002 and a second trio album with two Dutch players in 2010, and in February 2010 he was appointed a full-time practical music professor at the Seoul Institute of the Arts. In the 2010s he was the bassist of the veteran Korean Jazz First Generation band. The cover of his 2010 album prints his name as Jeon Seong Sik Trio, Discogs and MusicBrainz use the same spelling, the notes on Melon print Jeon Sung Sik, and Korean newspapers print only the Hangul.

Very little of his personal history is published. The Hankook Ilbo gave his age as 33 in October 2000; the same article gives his pianist Kwak Yoon-chan the same age, and OhmyNews says Kwak was born in 1968, so the header says "about 1968". No source found gives his birth date, his birthplace, his family or where he studied, and no interview with him was found.

The earliest trace is a Yonhap listing of May 21, 1996 for a month of evenings at the Post Theater in Sinchon, Seoul, in which the singers Kim Jun and Yun Hee-jung took the first and second halves of June, the pianists included Im In-gun, the saxophonists included Kim Soo-yeol, and the bass duties were shared by Jeon and a player named Kim Bong-bae. Bugs lists him on bass, with the trumpeter Juhan Lee, on one track of the ballad singer Seo Young-eun's album Softly Whispering I Love U (dated January 1998), and in April 1999 he is credited on bass on five tracks of the saxophonist Lee Jung-sik's album Hwadu: The Korean Jazz Standards Vol. 1, with Yoonchan Kwak on piano, Kim Hee-hyun on drums and Juhan Lee on brass. A 2003 OhmyNews profile of Kwak names Jeon, Lee Jung-sik and Juhan Lee as the leading Seoul musicians he had worked with since returning to Korea in 1996.

His first record as a leader came in September 2000. In a Hankook Ilbo interview of October 5, 2000, the 33-year-old Jeon described the score he had written for the mystery melodrama Vanishing Twin: 23 pieces of original jazz, the first film score of that kind in Korea, of which the CD carried 12, and, the paper added, the first album led by a Korean bassist. He wrote the music scene by scene, working from a calm, mysterious "purple" mood, and recorded it with a quartet of Kwak on piano, a saxophonist the article spells Son Seong-jae (probably Sungjae Son, who was also aged around 30 in 2000), and the American Chris Barga on drums and vibraphone, in a single day, September 13, 2000, at Nanjang Studio. The producers asked for vocals and he refused, because singing would have turned the music into accompaniment. The album runs through bebop, swing, funk, ballad, Latin and free jazz in an all-acoustic setting; he told the paper he preferred the more experimental tracks, the modal "Vanishing" and the free "무의식", and that he wanted Korean jazz players to write their own music so that countries like the United States and Japan would take Korean originals seriously. The film itself did poorly at the box office. The CD came out from Wawa Entertainment from October 10.

From 2002 he worked steadily as the bassist of Seoul's busiest players. On October 30, 2002 he played in a trio with the pianist Kim Kwang Min and Chris Barga (drums and vibraphone) at the Seoul Arts Center to a crowd of about 2,000; the Munhwa Ilbo reviewer liked the concert and only regretted that the contrabass was buried in the mix. A month later the paper Electronic Times reviewed his second album, Twilight, calling him Korea's best bassist: with Ulf Wakenius on guitar and Barga on drums and vibraphone, it holds eight pieces, six by Jeon, one by Wakenius and one by Barga, and the reviewer heard the bass speaking quietly and the guitar answering in whispers. In July 2003 he was one of the players behind the vocalist Malo for her release concerts at the Hanjeon Arts Full Center, alongside the harmonica player Jeon Jeduk, the pianist Mijung Lim (spelled Im Mi-jung in the notice), the guitarist Jeong Su-wook and Barga. In December 2003 and again in July 2004 he and Barga, whom the press calls an American jazz drummer, were billed with the pianist Ron Branton, and a Herald Business piece of June 2004 describes him as a member of the Ron Branton Trio. A Herald Business preview of May 2004 says he had played with Kenny G and Brian McKnight.

That year brought a run of dates. Blue Note Seoul announced a special week of Korean groups for May 10 to 15, 2004, with two acts a night, and billed his band to play the first set on Friday, May 14. The singer Nam Yeji's debut album Am I Blue? (June 2004) is reported by the Seoul Shinmun, Yonhap and the Kyunghyang Shinmun as using him among its session players, with the guitarist Sam Lee and the pianist Hahn Choong-wan. He gave two performances at the Rochester jazz festival in New York State on the 12th of that month, the Herald Business reported, and on August 19 and 20, 2004 he and the guitarist Kim Min-seok were the core of a "Brazilian Project" at the EBS Space series in Seoul. A TV guide of August 2006 lists a similar group, "Brazilian Colors", built around Kim Min-seok with Mijung Lim, Jeon, Barga and Kim Jeong-gyun. In September 2006 Newsis wrote that Mijung Lim had once led a jazz group called Nebraska with him.

The following years were steadier. In November 2005 he was billed on bass in the pianist Park Jong-hoon's concert at Konkuk University, with the saxophonist Son Seong-je, Barga and Kim Min-seok; in December 2005 he played the "Romantic Trio" concert with the haegeum player Kim Ae-ra and the Japanese pianist Isao Sasaki and, Yonhap said, took part in the recording of Kim's third album; and in December 2006 Yonhap noted the release of Park Jong-hoon's trio album Colors with Jeon and Barga. On January 5, 2008 EBS Space Gonggam showed him in a quintet with Yoonchan Kwak, the drummer Oh Jong-dae, Kim Min-seok and the saxophonist Son Seong-je, and Bugs dates a four-track set under his name, Moody's Mood For Love, to March 3, 2008 (distributor QUEEN): its notes call it a duet-sound single with Barga and the vocalist 여진, with whom the notes say he had made the album Double Rainbow. No listing of Double Rainbow was found.

On October 10, 2009 he was billed with Park Jong-hoon, Barga on vibraphone and a violist and string duo in a Beethoven program at the Yongin Keun Eoulmadang hall. In February 2010 Newsis reported that the Seoul Institute of the Arts had hired him as a full-time professor in its practical music arts school, with Barga among the adjunct appointments, and described him as having played with Kim Kwang Min, the sopranos Sumi Jo and Shin Young-ok and Kenny G, and as leading his own band. In July 2010 the saxophonist Ben van den Dungen and the pianist Kris Goessens, two Dutch musicians, took part in a jazz summer school at the school, and that November he released Memories of the Hague with them as the Jeon Seong Sik Trio. All seven pieces are his own compositions and arrangements; the notes on Melon, by the critic Kim Hee-jun, place the recording in the small Dutch village of Zeist. Discogs lists the CD on Audioguy Records, catalog number AGHSCD0004, and Yes24 gives the label as Joeun Music. That August his trio also contributed "길 (The Road)" to the soundtrack of Nam Mu-seong's documentary Bravo! Jazz Life, where he is also billed on "Moonglow" with the first-generation band of Shin Kwan-woong, Kim Soo-yeol, Choi Sun-bae, the clarinetist Lee Dong-gi and the drummer Im Heon-su.

That band became his main long-running association. Sat Economy listed him as its bassist for the UNESCO World Jazz Day concert at Olympus Hall in Samseong-dong on April 30, 2013, with the vocalist Nah Youn-sun; in March 2015 a KBS television concert show billed the band as Janus, with Shin, Choi Sun-bae, Lee Dong-ki, Im Heon-su, Kim Soo-yeol and Jeon on bass, joining the singers Park Sung-yeon and Woongsan. In February 2019 the Ajunews described him as the head of the Korean Jazz Creative Studio (한국재즈창작소) when he took part in a meeting between Paju city councillors and the band, and Shin Kwan-woong's profile records him on bass in a 2024 date at the Bottomline club. A 2019 exhibition notice about the teacher Lee Pan-geun names him among the musicians Lee influenced, and a 2005 review of the trio Triologue says that the guitarist Kim Min-seok recorded in the late 1990s with Oh Jong-dae, Im Mi-jung and Jeon; neither source gives details.

What is not known is most of the rest: his birth date and place, where he studied, who taught him, whether he has other albums, and what he is doing now beyond the dates above. This profile gives only what newspapers, record listings and music-service pages state.

His own words are few. In 2000 he said he preferred the free and modal tracks of Vanishing Twin and wanted Korean players to write original music. Of his playing, the Electronic Times review of Twilight heard a distant, lonely mood and a contemplative view of life, with the bass opening the conversation and the guitar replying quietly. The critic Kim Hee-jun's notes for Memories of the Hague call it modern jazz with a lyrical emphasis, slow to medium tempos and plain playing rather than complexity, aimed at listeners who are not jazz specialists; they describe the themes as tender, sad and at times mournful. Bugs files Twilight under fusion jazz.

No source names his teachers or his influences, and none describes his tone or technique, so nothing is said about them here.