Hiroko Kokubu (国府弘子, Kokubu Hiroko in Japanese order) is a Japanese jazz pianist, composer and arranger, born on August 26, 1959, in Shibuya, Tokyo. She studied piano at Kunitachi College of Music (国立音楽大学), where she first took to jazz, and after graduating she went to the United States on her own to study with the bebop pianist Barry Harris, a teacher named in her Japan Foundation and Yamaha profiles.

She came home and signed with JVC, and her major-label debut, More Than You Know, was released on October 21, 1987. The rhythm section is Ikuo Sakurai on bass and Motohiko Hino on drums, with Toshiyuki Honda playing soprano saxophone on two tracks. Kokubu wrote nine of the ten pieces; the tenth is Gilbert O'Sullivan's "Alone Again." Globetrotting with Hiroko Kokubu (1988) widened the sound with Fender Rhodes, guitar, flute and synthesizers, and two drummers, Yuichi Togashiki and Hino. On Point of No Return (1990) she orchestrated a sixteen-piece string section, and Light and Colour (1991) was co-produced by the Brazilian composer and guitarist Oscar Castro-Neves, a Latin-leaning record that Discogs tags Latin Jazz, Fusion and Smooth Jazz. Pure Heart (1992) followed, recorded and mixed by Allen Sides.

Her most visible partnership of the early 1990s was with the guitarist Kiyotsugu Amano. She played piano on his albums Azure (1991) and Branché (1992), and in 1993 the two made Heaven, with the American players Abraham Laboriel on bass, Alex Acuña on drums and percussion, Don Grusin on synthesizer and Gary Herbig on saxophone and flute. A second record, Heaven and Beyond..., came out in 1995, and Japanese Wikipedia refers to the pair's work together as the "Heaven" project.

The records of the late 1990s were built around her own writing and a more varied band. Bridge (1997) is mostly her own compositions plus a reading of "Bridge Over Troubled Water." Diary (1998) has the horn section Big Horns Bee, the flutist Rie Akagi, the bassist Yoichi Yahiro, the drummer Masayuki Muraishi and the singer Anri on one track, and its set list runs from the Beatles' "Drive My Car" and "Lucy in the Sky with Diamonds" to Emerson, Lake and Palmer's "Tarkus: Eruption - Stones of Years." In the same years she was a sought-after guest. She played piano and pianica on the group Forma De Agua's Jeito Do Brasil (1998), piano on the drummer Shuichi Ponta Murakami's version of "Mambo No. 5" on Welcome to My Life (1998), and arranged and played "My Romance" and "Israel" for the 2000 tribute Memories of Bill Evans, a salute to Bill Evans. She also wrote the Japanese liner notes for a 1999 Miles Davis compilation, Love Songs.

From 1999 she turned increasingly to solo and trio piano. Piano Letter (1999), Piano Tapestry (2001) and Piano Voices (2003) are largely solo, the second with arrangements of "Maiden Voyage," "Scarborough Fair," "Over the Rainbow" and "What a Wonderful World." New York Uncovered (2004) is a trio date with Christian McBride on bass and Mino Cinelu on drums and percussion. Hola! (2007), made with her regular trio of Yoichi Yahiro on bass and Tappi Iwase on drums, is a Latin-flavored set that the Japan Foundation profile calls her signature release; the same profile says the trio marked its fifteenth anniversary in 2013. In 2007 she was also a guest pianist on Kaori Kobayashi's Glow, and in 2008 she shared Heart Cocktail Again with Naoya Matsuoka, Toshiaki Otsubo and Rie Akagi, each contributing music and arrangements. Otsubo, a keyboardist, is her husband and has produced several of her records.

The 2010s and 2020s have brought a solo album, Piano Iccho! (January 21, 2015); a duo record of songs with the vocalist Hiromi Iwasaki, Piano Songs (2016); and a trio album with Yahiro and Iwase, Piano Party (February 19, 2020). The Japan Foundation counted 21 albums by 2014. In October 2025 she was announced for the Hamamatsu Jazz Week, with a lecture concert on October 24 at Kajimachi Yamaha Hall of classical pieces by Chopin, Mozart, Mendelssohn and others in her own jazz arrangements. She turned 67 in August 2026, and 2027 will mark forty years since her debut.

Alongside the records she has a long public profile in broadcasting and teaching. According to Japanese Wikipedia she has hosted the Yamano Big Band Jazz Contest since 1992, was a biweekly host of Jazz Tonight on NHK-FM, taught a jazz-piano series on NHK Educational Television in 2008, and began hosting a radio program on tbc Radio in January 2026. She is a visiting professor at Heisei College of Music and Shobi Gakuen University, a cultural ambassador for the city of Kawasaki, and a recipient of the Kawasaki City Cultural Award for 2019 (the 48th).

Kokubu is a classically trained pianist who found her way into jazz and then built a career on moving between idioms. Her jazz training came from the bebop pianist Barry Harris, and her records draw on classical repertoire, Latin and Brazilian rhythms, blues and pop and rock material. Discogs tags her albums across Fusion, Smooth Jazz, Latin Jazz and Contemporary Jazz, and the Japan Foundation describes a distinctive style that crosses genres. She writes much of her own material, with a taste for dance rhythms (the bossa nova, samba and rumba of Light and Colour and Hola!) and for songs everybody knows ("Mrs. Robinson," "Englishman in New York," "La Isla Bonita," "Drive My Car").

It is fair to say that her career has a popular-music side as well as a jazz-club side. She has recorded with the pop singers Hiromi Iwasaki and Anri, appeared as a guest at a 2011 benefit concert by the singer Epo, and works as a television and radio presenter. Her catalog nevertheless sits almost entirely in jazz: Discogs files nearly every album under Jazz, her records are piano-trio and solo-piano dates, she trained with a jazz pianist, and her teaching and broadcast work is about jazz piano.