Background & Aims: Bariatric surgery might reduce overall mortality from obesity. We investigated whether the survival times of patients who have had bariatric surgery are similar to those of the general population and are longer than of obese individuals who did not receive surgery. Methods: We performed a population-based cohort study of persons with a diagnosis of obesity listed in nationwide registries from Nordic countries from 1980 through 2012. Bariatric surgery was analyzed in relation to all-cause mortality and the obesity-related morbidities cardiovascular disease, diabetes, cancer, and suicide. Poisson models provided standardized mortality ratios (SMRs) with 95% confidence intervals (CIs). Multivariable Cox regression provided hazard ratios (HRs) for mortality in participants who did and did not have surgery. Results: Among 505,258 participants, 49,977 had bariatric surgery. Overall all-cause SMR was increased after surgery (1.94; 95% CI, 1.83–2.05) and increased with longer follow-up, to 2.28 (95% CI, 2.07–2.51) at ≥15 years after surgery. SMRs were increased for cardiovascular disease (2.39; 95% CI, 2.17–2.63), diabetes (3.67; 95% CI, 2.85–4.72), and suicide (2.39; 95% CI, 1.96–2.92) but not for cancer (1.05; 95% CI, 0.95–1.17); SMRs increased with time. In obese participants who did not have surgery, all-cause SMR was 2.15 (95% CI, 2.11–2.20), which remained stable during follow-up. Compared with obese participants who did not have surgery, patients who had bariatric surgery had decreased overall mortality from all causes (HR, 0.63; 95% CI, 0.60–0.66), cardiovascular disease (HR, 0.57; 95% CI, 0.52–0.63), and diabetes (HR, 0.38; 95% CI, 0.29–0.49) but increased mortality from suicide (HR, 1.68; 95% CI, 1.32–2.14). Cancer mortality was decreased overall (HR, 0.84; 95% CI, 0.76–0.93) but increased at ≥15 years of follow-up (HR, 1.20; 95% CI, 1.02–1.42). Conclusions: In a study of persons with a diagnosis of obesity listed in nationwide registries of Nordic countries, we found that obese patients who have bariatric surgery have longer survival times than obese individuals who did not have bariatric surgery, but their mortality is higher than that of the general population and increases with time. Obesity-related morbidities could account for these findings.