Alcohol consumption contributes to over 200 diseases and conditions and has severe socioeconomic consequences for both individual consumers and the society in which they live. If left unchecked, alcohol misuse can develop into an addiction. Previous research has identified stress and impulsivity (i.e., the tendency to act in haste and without foresight) as key risk factors for alcohol misuse and addiction. Furthermore, prior work has shown that impulsive behaviour strengthens acute psychosocial stress–induced alcohol craving and consumption. However, both stress and impulsivity are multifaceted and relatively little is known about how different measures of impulsivity or different stressors effect the stress– impulsivity–alcohol pathway. Therefore, the overall aim of this thesis was to better understand the impact of impulsivity on alcohol use in the context of acute, chronic, and cumulative lifetime stress. Specifically, the hypothesis that the effects of stress on alcohol use behaviour would be strengthened by impulsivity was tested across several studies ranging from experimental studies to large–scale national cohort approaches. First, drinking behaviour was assessed in response to acute physical, psychosocial, and mixed stressors. It was found that heightened negative urgency (i.e., the tendency to act rashly under extreme negative emotions) and negative affect were associated with increased levels of alcohol craving. Second, the COVID–19 pandemic was utilised to understand the impact of chronic stress on alcohol use behaviour, finding that stress and impulsivity were both independently associated with increased alcohol use behaviour. However, the direction of the negative affect and personality interactions went in the opposite direction to that which was predicted in the primary hypothesis of this thesis. Finally, the main hypothesis of this thesis was tested and extended in the context of cumulative lifetime stress. It was hypothesised that the association between cumulative lifetime stressor exposure and lifetime alcohol use would be mediated by emotional dysregulation, and that increased impulsivity would strengthen these relationships. The data supported these predictions and negative urgency was found to be a critical moderator, strengthening these relationships. Overall, this thesis provides a nuanced overview of stress–impulsivity interactions in terms of alcohol use and highlights the importance of negative urgency and emotional regulation in these relations.