Julien Lourau was born in Paris on March 2, 1970, the son of the sociologist René Lourau. According to AllMusic he took up the saxophone at eleven, played rock and roll at first and by fifteen was playing jazz-rock fusion. Sidney Bechet, Steve Lacy, Stanley Turrentine and Julius Hemphill are named among his early influences, with Joe Lovano and Wayne Shorter cited in later interviews.

In 1990 he joined the pianist Bojan Z and the guitarist Noël Akchoté in the electric quartet Trash Corporation, a group inspired by Ornette Coleman's harmolodic theory, and from it grew the Julien Lourau Groove Gang in 1992. That year he won the soloist prize at the Concours national de jazz de La Défense. The Groove Gang, a shifting line-up built around the trombonist Daniel Casimir and the trumpeter Nicolas Genest, recorded Groove Gang (Label Bleu, 1995) and City Boom Boom (Warner Jazz, 1998), and Lourau folded it in 1998. Meanwhile he was in demand as a sideman. He played tenor on Laurent Cugny's Big Band Lumière album Dromesko, was on Bojan Z's first quartet record, recorded in December 1993 and produced by Dave Liebman, joined Henri Texier's Soñjal Septet and, according to French Wikipedia, worked with Marc Ducret; Discogs also lists him among the members of the Orchestre national de jazz. A stretch of roughly two years with Abbey Lincoln, beginning on her 1995 album A Turtle's Dream, raised his profile abroad, and he is also on her Who Used to Dance (1997) and It's Me (2003). In 1996 he put out an album with the collective Olympic Gramofon, a group with the cellist Vincent Segal, the drummer Cyril Atef and the DJ Shalom.

From 1999 he turned toward electronics, working with the keyboardist Jeff Sharel, and the result was Gambit (Warner Jazz, 2000), whose track list includes pieces recorded live in Ouagadougou and in Kingston, Jamaica. It drew a young audience to his concerts, and in 1999 he won the jazz prize at the Victoires de la Musique, listed as jazz revelation of the year. A run of tours that began in 1999 took him through Central and South America, Africa and Europe.

In 2001 he returned to Label Bleu and to acoustic jazz with The Rise, on which Bojan Z, Henri Texier and the drummer Ari Hoenig share the stage with Latin percussionists. All About Jazz's reviewer heard Eastern European, African and Latin American strands merging, and Lourau himself wanted the record to be "soft and full of hopes." His next records mixed formats: the two-part electric project Fire & Forget (Label Bleu, 2005), produced by Jeff Sharel with Bojan Z on Fender Rhodes; Julien Lourau VS Rumbabierta (Label Bleu, 2007), made with Cuban percussionists and singers; and Brighter Days (Comet Records, 2008). In 2007 he formed Quartet Saïgon, named for the city in Vietnam where it made its debut, with the pianist Laurent Coq, the bassist Thomas Bramerie and the drummer Otis Brown III. Its album Quartet Saïgon (Naïve, recorded in 2008, released in 2009) splits the writing evenly between Lourau and Coq, and All About Jazz then described him as Marseille-based.

His duo with Bojan Z dates back to 1997, when the pair first played together at the Pannonica club in Nantes. After a crowdfunding appeal in 2014 they recorded the live album Duo at Le Triton in Les Lilas in May 2014, released in 2015. In 2017 he released Julien Lourau & The Groove Retrievers (2birds1stone), a funk-and-Latin album with a band that includes the baritone saxophonist Céline Bonacina and the pianist Robert Mitchell, and in the 2020s he has made two tribute albums for the Paris label Komos: Power of Soul: The Music of CTI (2021), recorded at Studio Pigalle in January 2021 with the keyboardists Arnaud Roulin and Léo Jassef, the bassist Sylvain Daniel and the drummer Jim Hart, and Crianças: The Music of Wayne Shorter (2023), recorded in April 2023. He is also the tenor saxophonist on the pianist Christophe Imbs's Soft Power (2023), with the drummer Anne Paceo, and a 2024 DVD from Le Triton captures the trio of Lourau, Bojan Z and the guitarist Nelson Veras.

Lourau plays tenor and soprano saxophones, with alto and baritone on some projects, and he has named Sonny Rollins and Wayne Shorter as influences, alongside the early heroes Sidney Bechet, Steve Lacy, Stanley Turrentine and Julius Hemphill. His writing draws on the blues, Latin music and the folk forms of both western and eastern Europe, and AllMusic reports that in interviews he said he preferred to seek audiences in Eastern Europe, Japan and South America rather than the United States. All About Jazz calls his playing lyrical and melodic with a pleasing economy, particularly on soprano, while capable of freer and more aggressive work. His career has moved between funk-jazz (the Groove Gang), electronics (Gambit, Fire & Forget), Afro-Cuban and Latin material (The Rise, Rumbabierta) and straight-ahead quartet writing (Quartet Saïgon), and the album Duo includes a piece by Ornette Coleman, a nod to the Coleman inspiration behind Trash Corporation. The electronic and fusion strands sit inside a body of work that is rooted in jazz improvisation.