PURPOSE: Physician wellbeing is critical to high-quality sustainable healthcare and optimal patient experience. Few objective measures exist to assay wellbeing (as opposed to just pathology) in surgery, or to evaluate the efficacy of wellbeing interventions. Flourishing (as measured by the Mental Health Continuum, MHC) has been suggested as a concise measure of global wellbeing in surgeons. We aimed to establish validity evidence for flourishing in a large national sample of surgical trainees, explore differences by gender and race, and confirm support for the underlying constructs. METHODS: This cross-sectional study of all General Surgery residents at 16 ACGME-accredited academic programs included an online survey of published measures distributed in February 2021. The Mental Health Continuum (MHC), a three-factor model, assesses emotional, social, and psychological wellbeing and is an established metric of psychosocial thriving in non-physicians. A global score cut-off exists for flourishing which represents high wellbeing. Correlation between flourishing and established measures of risk and resilience in surgery were assessed for validity evidence. Differences by gender and race were explored. A confirmatory factor analysis (CFA) was performed to confirm the three-factor structure in surgical trainees. RESULTS: 300 residents (60% non-male, 41% non-white) responded to the survey. For the overall group, flourishing was significantly positively correlated with all wellbeing resilience factors and negatively correlated with all risk factors. This held true for race and gender subgroups based on interaction analyses. CFA and sensitivity analysis results supported the three-factor structure. CONCLUSIONS: Our findings offer validity evidence for flourishing as a measure of global wellbeing and confirm the three-factor structure of emotional, social, and psychological wellbeing in surgical trainees. Thus, the MHC may be a concise tool for assaying wellbeing, within and across subgroups, and for assessing wellbeing intervention effectiveness within the surgery.