This book constitutes the refereed proceedings of the 33rd International Conference on Databases Theory and Applications, ADC 2022, held in Sydney, Australia, in September 2022. The conference is co-located with the 48th International Conference on Very Large Data Bases, VLDB 2022. The 9 full papers presented together with 8 short papers were carefully reviewed and selected from 36 submissions. ADC focuses on database systems, data-driven applications, and data analytics.