The purpose of this study is to obtain additional long-term safety and efficacy data on the use of Inspire therapy. The study will be conducted in a post-market environment for the treatment of moderate to severe Obstructive Sleep Apnea (OSA) (20≤AHI≤65) in subjects who have been confirmed to fail or cannot tolerate positive airway pressure (PAP) treatments. Subjects meeting all baseline and pre-screening requirements will be implanted with the Inspire system. The Inspire implant process is conducted clinically through the patient's insurance plan. One-hundred and twenty-seven (127) study subjects will be implanted at up to 20 investigational sites in the United States. Subjects will be evaluated at baseline, implant, 1-, 2-, 6- and 12- months post-implant, and bi-annually thereafter through 5 years of post-implant follow-up. Evaluations include questionnaires, medical history evaluation, and evaluation of effect of the Inspire treatment on the patient's sleep apnea. A single night in-lab Polysomnography (PSG) sleep study will be conducted at baseline, and at the 1 and 3 year follow ups. Two night home sleep testing (HST) will be conducted at the 2, 4, and 5 year follow ups. Compensation will be provided for time and travel for research visits.