Michael Gielen was born in Dresden in 1927 as the son of the actress Rose Steuermann and Joseph Gielen, later director of the Burgtheater in Vienna. The Nazi takeover forced the family into emigration, first to Vienna, later to Argentina.
As répétiteur at the Teatro Colón, Gielen met the great conductors of the time.
Not until 1950 did he return to Vienna to work as conductor at the Staatsoper, together with Clemens Krauss, Herbert von Karajan and Karl Böhm. The most important chapter in his career was Frankfurt am Main, where the cooperation with Ruth Berghaus, Hans Neuenfels, Jürgen Flimm, Harry Kupfer and Volker Schlöndorff, known as the »era Gielen« (1977–88).
In 1986 Gielen was awarded the Theodor-W.-Adorno-Preis of the city of Frankfurt on the Main. In 2006 he received the Musikpreis of the city of Duisburg, in 2007 he has been honored with the Faust-Theaterpreis for his oeuvre and in 2010 he received the Siemens-Musikpreis. In 2005 he published his memoirs Unbedingt Musik.
Michael Gielen died in his house in Mondsee, Austria on 8 March 2019.