The aim of this study was to develop and validate an instrument to measure Belonging in Surgery among surgical residents. Belonging is the essential human need to maintain meaningful relationships and connections to one's community. Increased belongingness is associated with better well-being, job performance, and motivation to learn. However, no tools exist to measure belonging among surgical trainees. A panel of experts adapted a belonging instrument for use among United States surgery residents. After administration of the 28-item instrument to residents at a single institution, a Cronbach alpha was calculated to measure internal consistency, and exploratory principal component analyses were performed. Multiple iterations of analyses with successively smaller item samples suggested the instrument could be shortened. The expert panel was reconvened to shorten the instrument. Descriptive statistics measured demographic factors associated with Belonging in Surgery. The overall response rate was 52% (114 responses). The Cronbach alpha among the 28 items was 0.94 (95% CI: 0.93-0.96). The exploratory principal component analyses and subsequent Promax rotation yielded 1 dominant component with an eigenvalue of 12.84 (70% of the variance). The expert panel narrowed the final instrument to 11 items with an overall Cronbach alpha of 0.90 (95% CI: 0.86, 0.92). Belonging in Surgery was significantly associated with race (Black and Asian residents scoring lower than White residents), graduating with one's original intern cohort (residents who graduated with their original class scoring higher than those that did not), and inversely correlated with resident stress level. An instrument to measure Belonging in Surgery was validated among surgical residents. With this instrument, Belonging in Surgery becomes a construct that may be used to investigate surgeon performance and well-being.