Merging together several fields – literature, human sciences and psychiatry – this dissertation on Octave Mirbeau (1848-1917) focuses on a transitional period (end of the 19th century - beginning of the 20th). For centuries, the concept of alienation, which appeared in Europe in the 13th century, was widely used (in the Law as in philosophy, psychology,psychiatry, politics and literature). The origin of the word is Latin (alius, other people, and other people’s property was referred to as alienus, inalienable). Over the centuries, it became a negative term : what was different or belonged to someone else was seen as potentially dangerous. Mental illnesses, which restrict freedom, were regarded as alienating, and in the 19th century psychiatrists were called alienists. Philosophers and politicans (eg. Merx) also used the concept to detect the factors which enslaved human beings. Alienation was perceived as the basis of a system undermining fundamental liberties (social, economic or religious factors). Alienation, which is the central core in Mirbeau’s novels, mirrors some essential aspects of France at that time. Focusing on his novels from Le Calvaire (1886) to Dingo (1913)this dissertation will endeavour to show that alienation is a dialectical tension underlining society. If is the very structure of Mirbeau’s body of work – a work which, without being unknown, is often misunderstood. Yet, alienation in ists variousmeanings gives a strong unity to the work : “original” (family, education, Roman Catholicism and the values of society), psychiatric alienation (eg. L’Abbé Jules and Le Calvaire), artistic alienation (the agony of the writer). Alienation may therefore lead to its opposite – freedom regained through the great power of wrinting.