Hillai Govreen (also credited as Hillai Govreen-Segal) was born and raised in Israel; no source publishes an exact birth date or city. She started classical piano at six and took up clarinet at twelve under Professor Michael Gurfinkel, going on to play first clarinet in the Young Israel Philharmonic Orchestra. She won America-Israel Cultural Foundation scholarships for four consecutive years in high school (2012–2016), received the Israel Defense Forces' "Outstanding Musician" honor during her service, and won a full scholarship to the Barenboim-Said Akademie in Berlin.

She graduated with honors from The New School for Jazz and Contemporary Music in May 2020, studying clarinet under Anat Cohen and saxophone under Chris Cheek, with additional coursework under Mike McGinnis, Tony Malaby, Billy Harper, Steve Cardenas and Reggie Workman. She is a listed endorsing artist for P. Mauriat clarinets and saxophones, and has toured India, Europe, Israel and the United States, performing at venues including Dizzy's Club, The Jazz Gallery, Smalls, Mezzrow, Birdland and National Sawdust.

Her debut recording, Allusions (2021), is a clarinet-and-piano duo with pianist Nitsan Kolko, a fellow New School-trained, Israel-connected musician now also based in Brooklyn; recorded in the winter of 2020 and released July 1, 2021, it was praised by outlets in Belgium, Israel, Japan and Turkey. A 2024 single, "Face Down in the Dirt," recorded live at Ornithology in New York, featured trumpeter Greg Glassman, pianist Yago Vazquez, bassist Ben Meigners and drummer Willie Bowman. Her debut solo album, Every Other Now, was released August 1, 2025 on the respected Fresh Sound New Talent label (catalog FSNT-705), written in close partnership with bassist-composer Ben Meigners and recorded at The Bunker Studio, Brooklyn, in August 2024. The nine-track record features pianists Noah Stoneman and Eden Ladin, guitarist Steve Cardenas, drummers Eric McPherson and William West, percussionist Café Da Silva, and trumpeter Greg Glassman, and closes with two standards, Harold Arlen's "Ill Wind" and Richard Rodgers's "This Nearly Was Mine." All About Jazz's review said the record "establishes her as a vital new presence in contemporary jazz," comparing her tenor tone to Stan Getz's lyricism, and noted that the two-part composition "The Day Of" / "The Day After" addresses the October 7 attacks.

Govreen's writing on Every Other Now moves between a soft, lyrical tenor sound — reviewers have reached for Stan Getz, Melissa Aldana and Eli Degibri as reference points — and a clarinet voice shaped by her classical training and her New School study under Anat Cohen, one of the instrument's most prominent contemporary jazz voices. Her earlier duo work with pianist Nitsan Kolko, built on spontaneous dialogue and material she's described as alluding to ancient fables, points to a chamber-music sensibility that carries into the more fully-arranged, band-format writing of her debut solo record.