It was a curious start for an actor to begin by founding his own theatre company before training in drama. After university studies in Russian, Guillaume Rannou worked with Éric Vigner before creating the street theatre collective Éclat Immédiat et Durable. He then attended the Conservatoire National Supérieur d’Art Dramatique.

Comedian, director, author and polyglot, Guillaume Rannou has always been involved in several activities at once: after collaborating on the writing of the play La Vérité en Pointure, based on a text by Jacques Derrida, he published J’ai!, a dramatic essay on rugby, or êtreaujapon which evoked his stay in the Land of the Rising Sun, where he performed in two plays by K. Kushida. During these shows, he played his two roles in the native language. He has also appeared in films, namely under the direction of Patrice Leconte.

Along with graphic designers David Poullard and Florence Inoué, he created the collective À-ce-qu’on-dit, which researches linguistic habits. In 2006, this collective published the book Précis de Conjugaisons Ordinaires taking everyday locutions and transposing them to the infinitive, before conjugating them into all modes and tenses.