Purpose: Intensive care unit (ICU) bed availability is key to critical patient care. In many countries, older patients generally account for a significant proportion of hospitalizations and ICU admissions. Therefore, considering the rapidly increasing aging population in South Korea, it is important to establish whether the demand for critical care is currently met by available ICU beds. Materials and Methods: We evaluated a 9-year trend in ICU bed supply and ICU length of stay in South Korea between 2011 and 2019 in a population-based cross-sectional analysis, using data from the Korean Health Insurance Review & Assessment Service and Statistics database. We described the changes in ICU bed rates in adult (≥20 years) and older adult (≥65 years) populations. ICU length of stay was categorized similarly and was used to predict future ICU bed demands. Results: The ICU bed rate per 100000 adults increased from 18.5 in 2011 to 19.5 in 2019. In contrast, the ICU bed rate per 100000 older adults decreased from 127.6 in 2011 to 104.0 in 2019. ICU length of stay increased by 43.8% for adults and 55.6% for older adults. In 2019, the regional differences in the ICU bed rate nearly doubled, and the ICU length of stay increased six-fold. The ICU bed occupancy rate in South Korea is expected to rise to 102.7% in 2030. Conclusion The discrepancy between the demand and supply of ICU beds in South Korea requires urgent action to anticipate future ICU demands.