["Japanese Psychological Research, EarlyView. ", "\nAbstract\nThe social identity approach to health in social psychology (the so‐called “social cure”) explores the capacity for group memberships that furnish people with a positive sense of social identity to enhance their health and well‐being. Online social identity mapping (oSIM) is a tool that allows individuals to represent their social identities graphically, providing insights into the quantity and quality of these group‐based connections. However, to date only an English version of oSIM has been available, and the tool has only been validated in Western cultural contexts. To address this gap, the present study aimed to validate oSIM in Japan. To this end, a sample of Japanese participants (N = 309) created a visual map of their social group memberships using oSIM and also completed measures of health, well‐being, loneliness and social connection. The study confirmed that oSIM measures are valid in the Japanese context and identified significant correlations with social support, mental health, and subjective well‐being. Findings also indicated that the quality of group memberships was a better predictor of loneliness and mental health than the number of groups to which a person belongs. This suggests that interventions targeting loneliness should focus on enhancing the quality of social group memberships and associated social identities rather than just increasing the number of a person's social ties. Findings also highlight the importance of oSIM being available in non‐English‐speaking countries to support the assessment and improvement of public health in the community.\n"]