<h3>Purpose</h3> Severe obesity, defined as body mass index (BMI) ≥ 40 kg/m<sup>2</sup>, is a contraindication for a heart transplant (HT). However, practice varies across transplant centers. This study examined the post-transplant survival of these patients who underwent HT in the United States. <h3>Methods</h3> We included adult patients who underwent HT between 2000 and 2018 in the Scientific Registry of Transplant Recipients with available BMI information. We compared 30-day, 1-, 5- and 10-year survival of those with a BMI≥ 40 kg/m<sup>2</sup> with BMI = 18.5-39.99 kg/m<sup>2</sup> using the Kaplan-Meier method. Cox proportional hazards regression models then determined the influence of BMI category on survival adjusting for known recipient and donor risk factors, including Index for Mortality Prediction After Cardiac Transplantation (IMPACT) score and predicted heart mass ratio. <h3>Results</h3> 36,115 adult HT recipients were included: 275 (0.8%) severely obese. The median (inter-quartile range) age was 55 (46, 62) years, and 25.4% were female. Severely obese patients had more hypertension (p=0.0019), diabetes (p<0.0001), and VAD use (p<0.0001). During a median follow-up of 4.1 (1.1, 8.3) years, 11,219 (30.3%) recipients died. Survival among severely obese compared to other groups was lower at 30-day, 1-, 5-, and 10-years (Figure; p<0.0001 for all). After adjustment for known risks, morbid obesity was associated with significantly higher post-transplant 30-day (HR 1.75, 95% CI 1.28-2.73; p=0.0125), 1-year (HR 1.44, 1.04-1.99; p=0.0260), 5-year (HR 1.27, 1.00-1.61; p=0.0541), and 10-year mortality risk (HR 1.31, 1.07-1.60; p=0.0094). <h3>Conclusion</h3> Survival following HT was significantly lower in recipients with severe obesity. Severe obesity should be addressed before HT is considered.