Marc Illich was born and raised in Feldkirch/Austria. His artistic career began during his studies in Vienna with the student theater "STUTHE". He was a longtime member of the improvisation ensemble "Quintessenz" and the free group "Studio Null Sieben" before he graduated from the Acting Academy Elfriede Ott in 2021. He worked in Vienna mainly with Peter Gruber at the Nestroy Spiele Schwechat and Bruno Max at the Theatre Scala.

Since the 2022/23 season he is a permanent ensemble member at the GSTT and also a freelance member of the Viennese group "Ensemble Ehrlos".

At the GSTT he has appeared as Trofimov in Chekhov's "The Cherry Orchard" (directed by Volker Schmidt), as the Narrator in "The Jungle Book" (directed by Razvan Mazilu), as Demetrius in "A Midsummer Night's Dream" after the work of William Shakespeare, directed by Kristóf Szabóund, in "The Snow Queen" by Yevgeny Schwartz, directed by László Béres, and in the title role in Wolfgang Hermsdorf's "Tschick. Why We Stole the Car", directed by Irisz Kovacs.