Psychological boundaries is a theoretical construct in psychology representing the conceptual limits or divisions individuals establish between their internal psychological state (thoughts, feelings, needs) and the external environment, including other people. This concept is fundamental to understanding self-differentiation and interpersonal dynamics. The research field investigates how individuals define, maintain, and regulate these boundaries, examining their impact on autonomy, vulnerability, emotional well-being, and relationship quality. Key characteristics include their varying degrees of permeability (rigid, porous, or flexible) and their role in mediating self-protection, personal integrity, and healthy interaction.