Keiko Matsui was born Keiko Doi in Tokyo on 26 July 1961. Her mother enrolled her in piano lessons shortly after her sixth birthday, and she studied classical piano through her school years before turning toward jazz and her own composing in junior high school. She read children's culture at Japan Women's University, and alongside that studied at the Yamaha Music Foundation, which is where her recording career actually begins: Discogs carries her, as Keiko Doi, on Junior Original Concert '76 Vol. 1~4, a Yamaha Music Foundation release from 1976, and on the Grand Prix album of the 1980 International Electone Festival.

Between 1981 and 1985 she recorded as one third of Cosmos, a trio of keyboard players made up of Yumiko Tanaka, Roman Kaieda and herself. Cosmos put out Hyoryu (1981), Can Can Can! and Bourbon Suite (1982), Musitopia and Spiral Dream (1983), the Lensman soundtrack and Musou Toshi (1984), and Session V (1985). The group's sound sat in the synth-funk and fusion territory that Japanese reissue culture has spent the last decade rediscovering, and in 2024 the label Konbini Klassics made the Cosmos track "Midnight Shuffle," from Bourbon Suite, the B-side of its first 7-inch, catalogue number KK 001.

Session V is the most revealing record of that period. It was cut at the Yamaha R&D Studio in Los Angeles between 7 and 16 December 1984, and its credit block puts Keiko Doi on keyboards next to drummer Chester Thompson, percussionist Ed Mann and Ian Underwood on programming, three musicians whose reputations were built in and around Frank Zappa's bands. She was 23.

Her solo debut, A Drop of Water, followed on Japan Record, with a US issue on Passport. It was produced by shakuhachi player Kazu Matsui, whom she met during the Cosmos years and married; he produced most of what she released for the next two decades and plays on a good deal of it. She signed to MCA for No Borders (1990), then moved through Pioneer, Canyon International and White Cat before Sapphire (1995) put her on the American chart in earnest, reaching No. 9 on Billboard's Top Contemporary Jazz Albums chart.

The Countdown Records years brought Dream Walk (1996), Full Moon and the Shrine (1998) and her first live album. Full Moon and the Shrine reached No. 2 on the same chart, with Marcus Miller, John Patitucci and Abraham Laboriel credited on bass samples and Kazu Matsui on shakuhachi. Then, in July 2001, her first record for Narada, Deep Blue, went to No. 1 on Billboard's Top Contemporary Jazz Albums chart and held the position for three weeks.

She has released steadily since: the Planet Joy years in Japan (The Piano, The Ring, Wildflower, Walls of Akendora, Compositions), White Owl for Narada, Moyo / Heart & Soul for Victor and Shout! Factory in 2007, and then a long run with Shanachie and Avex Trax that produced The Road... (2011), Soul Quest (2013), Journey to the Heart (2016), Echo (2019) and Euphoria (2023). Euphoria was released on 31 March 2023 and reissued on vinyl on 29 November 2024.

Alongside the records she has used releases as fundraising instruments. The 1997 mini-CD A Gift of Hope supported the Y-ME National Breast Cancer Organization. A Gift of Life went to the National Marrow Donor Program and to the Marrow Foundation's Asians for Miracle Marrow Matches campaign, which works on donor registration in communities where matches are hardest to find. The title track of Wildflower (2003) was given to the United Nations World Food Programme's work in Africa, and she performed at UN Headquarters in New York on 17 December 2003.

At 65 she continues to tour internationally. She played Yoshi's in Oakland on 25 August 2026 and is booked into City Winery in New York on 7 September 2026.

Matsui's playing sits at the meeting point of three things: a classical piano training that began at six, the Yamaha Music Foundation's electronic-keyboard and Electone culture, and the Japanese fusion and synth-funk of the early 1980s that she came up inside with Cosmos. Discogs files her records under Smooth Jazz, Fusion and Contemporary Jazz, and her earliest solo work also carries a Modern Classical tag, which is fair: melody-first writing, wide dynamic range, and a preference for a singing right hand over dense harmonic display.

The Japanese element in her sound is deliberate rather than decorative. Kazu Matsui's shakuhachi runs through many of the records as a lead voice, not a texture, and she plays shakuhachi herself on Deep Blue. Titles across the catalogue reach for the same imagery, from Cherry Blossom to Full Moon and the Shrine.

Her later records widen the frame. The Road... (2011) was co-produced with Cameroonian bassist Richard Bona. Journey to the Heart (2016) was built around a Latin rhythm section of Carlitos Del Puerto, Jimmy Branley and Luisito Quintero. Euphoria (2023) brought in arrangers John Beasley, Randy Waldman and Ron Pedley and a guest list drawn from across contemporary jazz.