The study design is a multi-site, prospective, open-label, non-randomized, single-arm clinical study to test the efficacy of the LinguaFlex Tongue Retractor for the treatment of moderate to severe Obstructive Sleep Apnea (OSA) (AHI ≥15 at baseline) in adult subjects in twelve (12) months of continuous use. The study will include three (3) investigational sites that will implant a maximum of eighty (80) subjects with the LTR. No single site is to perform more than 35 implants. After informed consent is obtained, eligible subjects (adults who have moderate to severe OSA) will be screened for study inclusion. The screening will consist of a Home Sleep Test (HST) completed within four (4) months of inclusion in the study to confirm the diagnosis of moderate to severe OSA, an Epworth Sleepiness Scale (ESS) assessment, Snoring Self-Assessment (SOS) with bed partner input (SBPS), assessment of pain, speech and swallowing, and a physical examination. The screening data will be reviewed by the Sponsor's designated study monitor to confirm and approve that inclusion criteria are fully met. Failure to meet all inclusion criteria will be designated as a screen failure and the subject's enrollment will be terminated. Participation in the study is voluntary. Subjects may withdraw at any time during the study. Reasons for the withdrawal will be recorded and entered into the clinical study report. Any subject who withdraws from the study for any reason will have the device removed and will undergo a Post Device Removal Follow-Up within 30 days (-7/+ 15) of device removal.