The study is dedicated to the exploration of the phenomenon of loneliness in contemporary psychological science. The authors conduct a comparative analysis of existing concepts of loneliness as presented in domestic and foreign literature, emphasizing the polysemy and complexity of this notion. Approaches from various scientific schools — philosophy, sociology, psychology — are examined, each offering its own understanding of loneliness. Special attention is given to the historical aspect of the problem, starting from ancient times and extending to the present day. Differences in the interpretations of loneliness by various thinkers, such as Hegel, Marx, Nietzsche, Sartre, Camus, and others, are highlighted. The authors note that the modern era is characterized by a new level of perception of loneliness due to the global spread of digital communications, which influence social behavior and the perception of individuality. The relevance of the study is determined by the necessity for an in-depth examination of the impact of loneliness on personal development and psychological well-being, especially among adolescents, whose inner world proves vulnerable to the negative consequences of loneliness. The methodology of the research includes a literary review of domestic and foreign publications, systematization, and critical analysis of existing approaches to defining loneliness. The main method is analytical-theoretical, allowing for the classification of scientists' views on loneliness and the formation of a working concept. Attention is given to the formulation of a clear working definition of loneliness that allows for a deeper understanding of the mechanisms of its emergence and experience. The scientific novelty of this research lies in the attempt to integrate contemporary views on the phenomenon of loneliness into a unified theoretical space, enabling a holistic understanding of the causes, mechanisms, and forms of experiencing loneliness. A deep comparative analysis of various approaches to understanding loneliness, including cultural, historical, and interdisciplinary contexts, has been conducted for the first time. The uniqueness of the study lies in identifying key factors that determine the emergence and consequences of loneliness in the digital age, as well as a detailed examination of the features of loneliness experiences among adolescents. The research complements existing knowledge by offering a new definition of loneliness based on an integrative approach, which emphasizes the role of personality traits, social conditions, and individual preferences in shaping the experience of loneliness. The findings expand the prospects for further empirical studies aimed at developing effective methods for preventing the negative consequences of loneliness and supporting young people during their personal development.