The PERMA-Profiler is a 23-item brief measure of flourishing, based on Seligman's PERMA model (Positive emotion, Engagement, Relationships, Meaning, Accomplishment). The measure was developed through three stages: item generation, factor structure confirmation, and psychometric testing. A large item bank was created, followed by item reduction to 15 core items, and the addition of eight filler items to assess overall wellbeing, negative emotion, loneliness, and physical health. The final measure was tested across 31,966 participants, demonstrating acceptable model fit, internal consistency, and validity. Scores are presented as a profile across domains, reflecting the multidimensional nature of flourishing. The PERMA-Profiler adds to the wellbeing measurement toolbox, allowing individuals to monitor their wellbeing across multiple psychosocial domains. It includes both positive and negative emotion items, acknowledging the importance of considering both aspects of mental health. The measure has good reliability and cross-time stability, and is suitable for use in various contexts. It provides a comprehensive assessment of wellbeing, with potential applications in research and practice. The PERMA-Profiler is a valid and reliable tool for assessing flourishing, offering a multidimensional perspective on wellbeing.The PERMA-Profiler is a 23-item brief measure of flourishing, based on Seligman's PERMA model (Positive emotion, Engagement, Relationships, Meaning, Accomplishment). The measure was developed through three stages: item generation, factor structure confirmation, and psychometric testing. A large item bank was created, followed by item reduction to 15 core items, and the addition of eight filler items to assess overall wellbeing, negative emotion, loneliness, and physical health. The final measure was tested across 31,966 participants, demonstrating acceptable model fit, internal consistency, and validity. Scores are presented as a profile across domains, reflecting the multidimensional nature of flourishing. The PERMA-Profiler adds to the wellbeing measurement toolbox, allowing individuals to monitor their wellbeing across multiple psychosocial domains. It includes both positive and negative emotion items, acknowledging the importance of considering both aspects of mental health. The measure has good reliability and cross-time stability, and is suitable for use in various contexts. It provides a comprehensive assessment of wellbeing, with potential applications in research and practice. The PERMA-Profiler is a valid and reliable tool for assessing flourishing, offering a multidimensional perspective on wellbeing.