In recent decades, opioid use has increased internationally and is a major public health concern. This study aims to characterize changes in opioid and other analgesic prescribing in Ireland over a 15-year period (2000-2015). This is a repeated cross-sectional study of administrative pharmacy claims data in 2000 and 2015. Individuals of all ages in Ireland's Eastern Health Board region who were eligible for the General Medical Services (GMS) scheme were included. This scheme covers 40% of the population, mostly those on lower incomes and older people. The primary outcome was dispensing of opioids, both prevalence of any use and rate per 1000 GMS eligible population (standardized to the 2015 population). Logistic regression was used to assess odds of opioid dispensing in 2015 versus 2000, controlling for demographic differences. The eligible study population was 364 436 in 2000 and 523 653 in 2015. In 2000, 19.4% of the eligible population had at least one opioid dispensing compared to 20.8% in 2015. The rate increased from 671 to 1098 dispensings per 1000 population. The increase was highest in the dispensing rates of codeine, tramadol, oxycodone, buprenorphine, and fentanyl. Compared to 2000, there was higher odds in 2015 of being dispensed a strong opioid (adjusted odds ratio 2.0, 95%CI 1.97-2.04) or long-acting formulation (3.75, 95%CI 3.58-3.92). Increased prescribing of opioids, particularly strong opioids, between 2000 and 2015 is evident in Ireland. This is concerning due to the potential for misuse, and opioid-related morbidity/mortality.