This book constitutes the proceedings of the 29th European Conference on Advances in Databases and Information Systems, ADBIS 2025, which took place in Tampere, Finland, during September 23-26, 2025.  The 14 full papers included in this proceedings book were carefully reviewed and selected from 66 submissions. The book also contains 4 tutorial papers. The selected papers span a large spectrum of topics in the broader field of data management focusing on Query Optimization, Explainable AI, Entity Resolution and Integration, Data and Machine Learning, Spatio-Temporal and Graph Data, and Data Sharing and Synthesis.