Purpose: Obstructive sleep apnea (OSA) is linked to increased glaucoma risk in middle-aged and older adults. However, little is known about associations between OSA and glaucoma-related optic disc parameters in young adults. We explored associations between overnight polysomnography-derived measures of OSA and the optic disc in young adults. Design: Cross-sectional cohort study. Participants: Eight hundred forty-eight adults 19 to 22 years of age. Methods: Participants underwent an ophthalmic examination that included OCT imaging of the optic disc and measurements of intraocular pressure, axial length, and refractive error. Participants then underwent an overnight polysomnography study that obtained measurements of apnea–hypopnea index (AHI), peripheral oxygen saturation level, and number of cortical arousals from sleep. Based on the AHI results, participants were grouped into no OSA (AHI < 5 events/hour), mild OSA (AHI ≥ 5 and <15 events/hour), moderate OSA (AHI ≥ 15 and <30 events/hour), or severe OSA (AHI ≥ 30 events/hour). Main Outcome Measures: Neuroretinal rim area, horizontal and vertical widths, and peripapillary retinal nerve fiber layer (RNFL) thickness. Results: The median AHI result across the study cohort was 2.2 events per hour (interquartile range, 1.0−4.4 events/hour). Based on the AHI results, 178 participants (21.0%) demonstrated OSA: 150 with mild OSA, 26 with moderate OSA, and 2 with severe OSA. In the unadjusted analyses, participants with OSA on average showed thinner peripapillary RNFL at the inferotemporal (P = 0.026) and superotemporal (P = 0.008) segments compared with those without OSA. Additionally, higher AHI results were associated with thinner RNFL superotemporally (P = 0.007). These findings remained significant after adjusting for gender, body mass index, ethnicity, and potential ocular confounders. There were no significant differences in optic disc measures between groups of OSA severity. Conclusions: Obstructive sleep apnea may be associated with preclinical thinning of the peripapillary RNFL in young adults. This suggests that an increased glaucoma risk already may be present in individuals with OSA since young adulthood. Long-term follow-up of this cohort will allow further optic disc changes in relationship to polysomnography parameters to be documented and associations with future glaucoma diagnosis to be explored.