Interpersonal relationship (or interpersonal relation) define a social association, connection, or affiliation between two or more persons. They vary in degrees of intimacy, self-disclosure, duration, reciprocity and power distribution. The main themes or purposes of the interpersonal relations are: family, kinship, friendship, love, marriage, business, employment, clubs, neighborhoods, ethical values, support and solidarity. Interpersonal relations may be regulated by law, custom or mutual agreement, and form the basis of social groups and societies. They appear when people communicate or act with each other within specific social contexts, and they thrive on equitable and reciprocal compromises.

The scientific analysis of interpersonal relationships involves several branches of the social sciences, e.g. communication, psychology, anthropology, social work, sociology, and mathematics. This scientific analysis had evolved during the 1990s and has become "relationship science," through the researches of Ellen Berscheid and Elaine Hatfield. This interdisciplinary science attempts to provide evidence-based conclusions through the use of data analysis.