INTRODUCTION: A significant proportion of patients with Crohn's disease (CD) and ulcerative colitis (UC) become opioid users, but data pertaining to predictors of chronic opioid use remain sparse. We examined predictors for chronic opioid use in CD/UC. METHODS: This is a nationwide cohort study based on Danish registries, comprising incident patients with CD/UC (>/= 18 years) from January 1, 1996, to December 31, 2021. Chronic opioid use was defined as >/= 1 prescriptions in at least 2 of 3 consecutive quarters. Cox regression models were used to estimate adjusted hazard ratios for predictors for chronic opioid use. Several variables and time-varying covariates (inflammatory bowel disease surgery, inflammatory bowel disease, and psychotropic medications) were included. RESULTS: In 15,092 patients with CD, 4,141 (27.4%) became chronic opioid users (median follow-up 7.35 years, 25%-75% percentiles [interquartile range] 3.40-13.66 years). The 3 most important predictors were surgery (4.20, 95% confidence interval [CI] 3.72-4.75), hypnotics/sedatives (2.02, 95% CI 1.81-2.25), and age >/= 50 years (1.92, 95% CI 1.77-2.09). In 30,416 patients with UC, 6,777 (22.3%) became chronic users (median follow-up 8.80 years, interquartile range 4.20-15.22 years). The 3 most important predictors were surgery (4.81, 95% CI 4.20-5.52), age >/= 50 years (2.62, 95% CI 2.44-2.82), and hypnotics/sedatives (2.11, 95% CI 1.95-2.29). DISCUSSION: An alarming proportion of patients became chronic opioid users. These results are helpful to risk stratify patients to prevent chronic opioid use. Clinicians should be particularly attentive in patients who have had surgery, who use hypnotics/sedatives, and who are elderly. We need evidence regarding pain management strategies, efficacy of nonopioid analgesics, and opioid cessation strategies.