Marc Illich was born and raised in Feldkirch, Austria. His artistic career began during his studies in Vienna, where he performed in the student theatre STUTHE. He was a member of the improvisation ensemble Quintessenz and the independent group Studio Null Sieben before completing his training at the Elfriede Ott Theatre Academy in 2021. He has worked in Vienna, notably with Peter Gruber at Nestroy Spiele Schwechat and with Bruno Max at SCALA Theatre. He is a permanent member of the GSTT ensemble since the 2022/23 season and is also a freelance member of the Viennese Ensemble Ehrlos.

At GSTT he can be seen as Trofimov in Chekhov's The Cherry Orchard (directed by Volker Schmidt), as the narrator in The Jungle Book (directed by Razvan Mazilu) and in the lead role in "Tschick - Why I Stole the Car", a stage adaptation by Robert Koall of Wolfgang Herrndorf's novel (directed by Irisz Kovacs).