Background: Excess alcohol intake and inherited predisposition may increase risk of atrial fibrillation (AF). We assessed the association between alcohol intake, polygenic predisposition to AF, and incident AF in the UK Biobank, a prospective cohort study. Methods: In 376 776 UK Biobank participants enrolled between 2006 and 2010, we tested alcohol consumption (stratified by the Centers of Disease Control and Prevention acceptable range of ≤98 g/wk for women or ≤196 g/wk for men; and as a continuous variable) and an AF polygenic risk score for association with incident AF. Results: Among participants (47.5% male, mean age 56.9 years), 6293 developed AF during a median of 6.9 years of follow-up. Alcohol consumption was associated with AF (hazard ratio, 1.10 [95% CI, 1.05–1.16] for intake above an acceptable range; hazard ratio, 1.04 per 100 g/wk [95% CI, 1.02–1.06]). An AF polygenic risk score was associated with AF (hazard ratio, 1.38 per SD [95% CI, 1.35–1.41]). In models including both alcohol and the AF polygenic risk score, each remained associated with AF. The 5-year cumulative risk of AF for individuals with alcohol intake above an acceptable range and in the highest decile of polygenic risk was 2.33% (95% CI, 2.07–2.59), compared with 0.69% (95% CI, 0.58–0.80) for those with alcohol intake within an acceptable range and in the lowest decile of polygenic risk. Conclusions: Alcohol consumption is associated with increased risk of AF across a range of polygenic predisposition to AF and adds to inherited and clinical predisposition to increase AF susceptibility. Preventive efforts focused on minimizing alcohol intake may be broadly applicable.