Abstract. The article is devoted to the problem of the phenomenon of prison loneliness. The relevance of this study is due to the fact that the phenomenon of prison loneliness underlies penitentiary stress, as a complex psychophysiological reaction of the body to being in a penitentiary space. One of the functions of the execution of punishment as a response of society to the unlawful actions of a criminal is punishment for a committed crime, which acts in the form of induction of mental suffering of a person as a result of his artificial separation from the usual social environment, the creation of prison loneliness. At the same time, the effect of transferring suffering from the body of the criminal to his soul, noted by M. Foucault, is realized. The purpose of the work involves the analysis of the phenomenon of loneliness in the conditions of places of deprivation of liberty. The main characteristic features of prison loneliness are described. It is shown that the punishment of a criminal by imprisonment, his forcible isolation from the mainstream society is based on the mechanism of creating artificial prison deprivation. It is noted that one of the attributes of punishing a criminal is the intentional creation of a special type of loneliness — prison, causing a high level of penitentiary stress. The article shows that two types of prison loneliness can be considered. The first one is proposed to be called “physical loneliness”, which is created by the physical isolation of the convict. At the heart of the generation of suffering of the personality of this type of loneliness is the effect of a violation of the human need inherent at the gene level to communicate with other members of society. This type of prison loneliness leads to a change in the psyche of the prisoner, the loss of communication skills, his slow emotional and mental degradation. The second type of prison loneliness (loneliness in the crowd) is characterized by the fact that in conditions of prison isolation, the prisoner is almost never left alone and is constantly under the influence of carriers of the penitentiary subculture, which has a powerful negative impact on the personality of the person serving the sentence. In an environment where interests are reduced to the satisfaction of vital needs, and interpersonal aggression is the norm of behavior, negative emotions prevail in the prisoner’s sense of self, the dominant of which will be a feeling of loneliness.