The study will be a multi-center, prospective, single-arm study conducted under a common implant and follow-up protocol. Twenty-one adolescents and young adults (10-21 years of age) with Down Syndrome with moderate to severe obstructive sleep apnea after adenotonsillectomy will be identified through a Multi-Disciplinary clinic for patients with Trisomy 21 at Massachusetts General Hospital's Hospital for Children, University Hospitals Rainbow Babies and Children's Hospital, Henrietta Egleston Hospital for Children, Cincinnati Children's Hospital, and Children's Hospital of Pittsburgh. Patients and their parents will be screened by a senior pulmonologist and pediatrician for medical clearance and willingness to participate. Subjects will then undergo preoperative evaluation with an in-lab polysomnogram (PSG), evaluation by a pediatric otolaryngology surgeon, and drug induced sleep endoscopy (DISE) to ensure all inclusion and exclusion criteria are met. Subjects meeting eligibility criteria will then be implanted with the Inspire® Upper Airway Simulation System, Model 3024 IPG, and any subsequent iteration thereof that are approved under P130008 for the treatment of obstructive sleep apnea, a hypoglossal nerve stimulator, after informed consent. Surgery will be performed by senior pediatric otolaryngologists who have completed a training program for the Inspire® system. Subjects will then adhere to a follow-up schedule. The device will be activated and settings titrated during an in-lab sleep study 1 month postoperatively. Quality of life surveys and device interrogation will be conducted at timed intervals. Subjects will then undergo in-lab polysomnography at 2 months, 6 months, and 12-months, then on an annual basis, and the device titrated as needed. All personnel adjusting device parameters will be trained in programming the Inspire® system. For this pilot study, we will evaluate safety and efficacy over the first year after device implantation.