Introduction: Obstructive sleep apnea (OSA) is a condition characterized by intermittent airway obstructions, leading to reduced oxygen levels and increased sympathetic nervous system activity. OSA can cause a range of health problems, including an increased risk of cardiovascular diseases and mortality. Galectin-3, a member of the galectin family, plays a significant role in inflammation and fibrosis. It is elevated in various conditions, including heart and lung diseases. The aim of this study was to determine whether galectin-3 levels are related to the severity of sleep apnea. Materials and methods: A total of 191 participant from University Clinical Hospital Center Bezanijska Kosa, Belgrade, Serbia, between January 2023, and May 2024. was included in the analyses. All patients have been hospitalized under suspicion of OSA, and they have all undergone a polysomnography test. Various demographic, respiratory, laboratory, and clinical parameters were obtained. Correlations between numerical variables and galectin-3 were assessed by the Pearson or Spearman correlation coefficient. Univariate and multivariate linear regression models were used to assess predictors of galectin-3 values. In all analyses, the significance level was set at 0.05. Results: The mean age of study participants was 56.2 years, mostly male (68.9%). Of comorbidities, two thirds of patients had hypertension (66.1%), 46.8% had hyperlipoproteinemia, and 21.1% had diabetes mellitus. Galectin-3 values significantly differed according to the examined groups (p=0.038), where patients who had an AHI of less than fifteen events per hour more often had lower values of galectin-3 in contrast to patients who had AHI of at least 15 events per hour, but fewer than 30 (p=0.019) and an AHI of at least 30 events per hour (p=0.046). In multivariate linear regression analysis significant independant predictors of higher galectin-3 values were older age, presence of coronary disease, hypoventilation syndrome, higher BMI, NTproBNP, lactate, creatinine, lower LDL, and lower FEV1 (p<0.05). Conclusion: The present study demonstrated that galectin-3 is linked to the severity of OSA and plays a crucial role in inflammation induced by intermittent hypoxia in OSA. Further screening and interventions targeting galectin-3 could aid in preventing inflammatory diseases related to sleep disturbances.