Background: Insomnia is the most prevalent sleep disorder; however, little research has explored the link between insomnia and atrial fibrillation (AF). Hypothesis: Insomnia is associated with increased risk of AF in a Chinese population. Methods: A total of 8371 Chinese participants (4314 males; mean age, 42.4 +/- 13.1 years) were enrolled in this cross-sectional study to investigate the association between insomnia and AF. AF was assessed in a standard supine resting position with a 10-s 12-lead electrocardiograph (ECG) or by self-reported history. Insomnia was assessed using the Athens Insomnia Scale (AIS), and a score of >= 6 was regarded as having insomnia. The association between insomnia and AF was determined by logistic regression analysis. Results: Among the 8371 subjects, 1074 (12.8%) had different degrees of insomnia, and AF was observed in 50 subjects (0.60%). After adjusting for potential confounders, individuals with insomnia had moderately increased likelihood of suffering from AF compared with those without insomnia (odds ratio [OR]: 1.92, 95% confidence interval [CI]: 1.00-3.70, P = 0.05). After stratifying data by age, a significant positive association was found in those age < 40 years (OR: 6.52, 95% CI: 1.64-25.83, P = 0.01), and a similar trend existed in males after stratifying by sex, although this relationship was not statistically significant (OR: 2.11, 95% CI: 0.92-4.83, P = 0.08). Conclusions: Individuals with insomnia may have a higher risk of AF in the particular Chinese population assessed in this study. Age (< 40 years) is a significant factor in the association between insomnia and AF.