Michel Portal was born on November 27, 1935 in Bayonne, in the French Basque Country, into a musical family. He started on the clarinet at the age of eight, at the town's music school, and played in local folk groups and chamber orchestras while also picking up the bandoneon. His interest in jazz began with radio broadcasts after the Second World War. At the Paris Conservatoire he studied clarinet and conducting with Pierre Dervaux and won the first prize in clarinet in 1959. In 1963 he won the international music competition in Geneva and the Swiss Jubilee prize, which sets out the two tracks he would follow for the rest of his life: a concert clarinettist with a classical training, and a jazz improviser.

His first professional years were spent in dance bands and light music, with the bandleaders Henri Rossotti, Benny Bennett, Raymond Fonsèque and Aimé Barelli, with Pérez Prado during a stay in Spain in 1958, and for a long period with the singer Claude Nougaro. His first recordings as a sideman, in the early and mid 1960s, show how quickly the Paris studios took him up: bassist Pierre Michelot's Round About a Bass (1963), Serge Gainsbourg's Gainsbourg Percussions (1964), a 1964 album by violinist Jean-Luc Ponty, albums by the singer Barbara, Jef Gilson's big band, and Claude Bolling's Jazzgang Amadeus Mozart (1965). On March 13, 1964 he played at the Salle Wagram in a benefit concert for the ailing Bud Powell. In 1965 he was in pianist François Tusques's sextet on Free Jazz, a landmark of European free jazz, and in 1966 he took part in André Hodeir's jazz cantata Anna Livia Plurabelle. The Académie du Jazz gave him its Prix Django-Reinhardt in 1968.

The years from 1969 to 1973 produced the records that made his name in jazz. Our Meanings and Our Feelings (Pathé), recorded in Paris on June 27, 1969, brought him together with bassist Jean-François Jenny-Clark, the drummers Aldo Romano and Jacques Thollot and the pianist Joachim Kühn, with Portal on tenor saxophone, clarinets and exotic instruments such as the taragot. The same year he played in Diego Masson's ensemble Musique Vivante on Luciano Berio's Laborintus 2 and on Karlheinz Stockhausen's Aus den sieben Tagen, and he co-founded the improvising group New Phonic Art with the trombonist Vinko Globokar. Alors!!! (Futura, 1970), recorded with John Surman, the bassist Barre Phillips, the drummer Stu Martin and the percussionist Jean-Pierre Drouet, is described by French Wikipedia as one of the first records to free European jazz from North American models by joining free jazz with contemporary European music. In 1971 he formed the Michel Portal Unit, a shifting group of European and American improvisers; its Châteauvallon festival concert of August 23, 1972 was released as À Châteauvallon: No, No But It May Be (1973). That same period he appeared on Pierre Boulez's Domaines with Musique Vivante and on albums by the drummer Sunny Murray and the bassist Alan Silva.

After Dejarme solo! (Cy, 1979), a record of solo reeds and bandoneon, and Arrivederci Le Chouartse with the drummer Pierre Favre and the bassist Léon Francioli (recorded live in Lausanne on October 3, 1980 and released on Hat Hut in 1981), he spent much of the 1980s on film music. AllMusic counts more than fifty film scores between 1969 and 2015, and he won three César awards for film music, for The Return of Martin Guerre (1983), Les Cavaliers de l'orage (1985) and Champ d'honneur (1988). He returned to jazz records with Turbulence (Harmonia Mundi, 1987) and Men's Land, and the live album 9-11 pm Town Hall, recorded at The Town Hall in New York on June 29, 1988, put him in a band with the drummer Daniel Humair, the pianists Martial Solal and Joachim Kühn, Jenny-Clark and the guitarist Marc Ducret. In the classical repertoire he recorded the Mozart clarinet concerto and quintet and the Brahms sonatas and quintets, premiered Franco Donatoni's clarinet concerto Portal in 1995 and a double concerto by Wolfgang Rihm in 2006, and was the subject of Jean-Louis Comolli and Francis Marmande's 1997 film Le Concerto de Mozart.

The 1990s and 2000s found him alternating between the two worlds and widening the circle of jazz partners. He recorded Festival de Lille, Novembre 1990 with Dave Liebman, the percussionist Trilok Gurtu and Mino Cinélu, duo albums with Martial Solal (Martial Solal Michel Portal, 1992, and Fast Mood, 1999) and with the accordionist Richard Galliano (Blow Up, 1997), Any Way (1993), on which the line-up changes from track to track and includes the trumpeter Kenny Wheeler, and Dockings (1998), a sextet record made in Amiens with the trumpeter Markus Stockhausen, Bojan Z, the bassists Steve Swallow and Bruno Chevillon and the drummer Joey Baron. Minneapolis (2001), made with the guitarist Vernon Reid, the pianist Tony Hymas and rhythm-section players associated with Prince, was a jazz-funk turn, and it was followed by the live Minneapolis We Insist! (2002). Birdwatcher (2007), recorded in Minneapolis with the saxophonist Tony Malaby, Tony Hymas and the percussionist Airto Moreira, won the Victoires du Jazz award for instrumental album of the year, and in 2005 the Académie Charles-Cros gave him its In Honorem prize for his whole career. Baïlador (2010), produced and arranged by the pianist Bojan Z, used guests from the American scene including Ambrose Akinmusire, Lionel Loueke and Jack DeJohnette. In 2011 he was named Commandeur of the Ordre des Arts et des Lettres.

His last decade stayed busy. Radar (2016) is a live duo with the pianist Richie Beirach, Eternal Stories (2017) was made with the Quatuor Ebène, and he played at Label Bleu's thirtieth anniversary concert in Amiens in 2017 with Henri Texier. For his eighty-fifth birthday he led a quintet with Bojan Z, bassist Bruno Chevillon, drummer Lander Gyselinck and trombonist Samuel Blaser, and the studio album MP85 (Label Bleu, 2021) won him a second Victoires du Jazz award for instrumental album. In 2019 his home town renamed its municipal theatre the Théâtre Michel-Portal, and in 2025 the book of interviews Le Souffle Portal, with Franck Médioni, and the film Quelques notes sur la liberté appeared. He passed away in Paris on February 12, 2026, at the age of 90; his agent announced his death to the press and his funeral took place on February 24 at the Père-Lachaise crematorium. A posthumous release, Mountain Call, a record by the bassist Miroslav Vitouš on which Portal plays clarinet and bass clarinet beside Jack DeJohnette, was recorded in Prague between 2003 and 2010 and came out on ECM on March 27, 2026.

Portal never settled in a single genre, and his instruments reflect that: clarinet and bass clarinet above all, with alto, tenor and sopranino saxophones, the bandoneon and the Hungarian tárogató as the other voices he used on record. He is considered one of the architects of modern European jazz, a player who took the freedoms of the American avant-garde (French Wikipedia hears the influence of the Chicago AACM musicians and Anthony Braxton on Alors!!!) and mixed them with the language of Boulez, Berio and Stockhausen, and later with jazz-funk and film music. He kept an equally serious career as a classical clarinettist, so he was never a jazz-only figure, but his recordings as a bandleader, from Our Meanings and Our Feelings to MP85, are overwhelmingly improvised music. The subgenre tags above describe only his jazz work, not his classical recordings or his film scores.