Background: The self-expanding, intra-annular Navitor (Abbott Structural Heart) valve includes an outer cuff to reduce paravalvular leak (PVL) and large stent cells for future coronary access. Objectives: The purpose of the PORTICO NG (Evaluation of the Portico NG [Next Generation] Transcatheter Aortic Valve in High and Extreme Risk Patients With Symptomatic Severe Aortic Stenosis) study is to evaluate the safety and effectiveness of the Navitor valve in patients with symptomatic, severe aortic stenosis who are at high or extreme surgical risk. Methods: PORTICO NG is a prospective, multicenter, global study with follow-up at 30 days, 1 year, and annually through 5 years. The primary endpoints are all-cause mortality and moderate or greater PVL at 30 days. Valve Academic Research Consortium-2 events and valve performance are assessed by an independent clinical events committee and echocardiographic core laboratory. Results: A total of 260 subjects were treated at 26 clinical sites across Europe, Australia, and the United States between September 2019 and August 2022. The mean age was 83.4 ± 5.4 years, 57.3% were female, and the average Society of Thoracic Surgeons score was 3.9% ± 2.1%. At 30 days, the rate of all-cause mortality was 1.9%, and no subjects had moderate or greater PVL. The rate of disabling stroke was 1.9%, life-threatening bleeding was 3.8%, stage 3 acute kidney injury was 0.8%, major vascular complications were 4.2%, and new permanent pacemaker implantation was 19.0%. Hemodynamic performance included a mean gradient of 7.4 ± 3.5 mm Hg and an effective orifice area of 2.00 ± 0.47 cm². Conclusions: The Navitor valve is safe and effective for the treatment of subjects with severe aortic stenosis who are at high or greater risk for surgery, which is supported by low rates of adverse events and PVL. (Evaluation of the Portico NG [Next Generation] Transcatheter Aortic Valve in High and Extreme Risk Patients With Symptomatic Severe Aortic Stenosis [PORTICO NG]; NCT04011722)