Marc Illich was born and raised in Feldkirch/Austria. His artistic career began during his studies in Vienna with the student theatre "STUTHE". He was a long-time member of the improvisation ensemble "Quintessenz" and the independent group "Studio Null Sieben" before graduating from the Elfriede Ott Theatre Academy in 2021. He has worked in Vienna with Peter Gruber at Nestroy Spiele Schwechat and with Bruno Max at Teatro Scala.

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

He appeared in A.P. Chekhov's The Cherry Orchard as Trofimov; Rudyard Kipling's The Jungle Book as the Storyteller; William Shakespeare's A Midsummer Night's Dream as Demetrius; Yevgeny Schwarz's The Snow Queen as the Robber; TSCHICK. Why We Took the Car by Wolfgang Herrndorf in the title role; The Theatre by Pascal Rambert as Sven; The Dragon by Yevgeny Schwarz as Heinrich.

At GSTT he worked with Volker Schmidt, Răzvan Mazilu, Kristóf Szabó, László Béres, Irisz Kovacs, Pascal Rambert, Yuri Kordonsky.