Coming from a family of artists (his brothers are comic artists as well), Marc-Renier Warnauts adopted his first name as his pseudonym. He studied at the Saint Luc Institute in Liège for three years. From 1982 on, he created several short fantasy stories for the magazines Tintin and Super Tintin. In 1983, his first albums appeared: 'Le Crapaud' (Ed. Jonas) and 'Le Reflet' (Ed. du Miroir). These two works established Warnauts as a comic artist of the Clear Line style. Specializing in rural stories, he continued with the titles 'Les Yeux du Marais' (1985), 'Le Cridu Faucon' (1987) and 'La Danse de l'Ours' (1989).
Marc-Renier worked with other writers as well, creating 'La Nuit des Frelons' with Gérard Dewamme in 1986, and 'Jackson' with Frank Giroud in 1989. This western appeared in the magazine Hello Bédé and later in album format. In 1990, he published 'Shosha', and started the series 'Le Masque de Fer' with writers Patrick Cothias and Goué-Dard. In 1991, 'Coeur Mange' with Denis Lapière appeared in print. For a while, he worked as a colorist on the new editions of 'Corentin' by Paul Cuvelier.
He collaborated with his brother Éric Warnauts on 'Ombres et Désirs' in À Suivre (1994) and 'Là où Meurent les Anges' (1997). In 1999, Marc-Renier teamed up with Yves Swolfs and launched the western 'Black Hills 1890' for Glénat. In 2006, he illustrated 'Le dernier visiteur de George Sand', a comic written by Rodophe and published in the collection Monum of Editions du Patrimoine.