The four-volume set LNCS constitutes the refereed proceedings of the 9th International Joint Conference on Web and Big Data, APWeb-WAIM 2025, held in Shenyang, China, during August 28-30, 2025.

The 136 full papers and 15 short papers presented in these proceedings were carefully reviewed and selected from 472 submissions. The papers are organized in the following topical sections:

Part I: Data Mining I; Machine Learning I; Information Retrieval and Knowledge Management I; Graph Data Management andAnalytics I; Complex Data Management.

Part II: Complex Data Management; Spatial and Temporal Data Management; Data Privacy and Trusted AI; Data Management on New Hardwares; Query Processing and Optimization; Data Mining II.

Part III: Data Mining II; Machine Learning II; Information Retrieval and Knowledge Management II; Graph Data Management andAnalytics II; Big Data Management.

Part IV: Big Data Management; LLM for Data Management; Information Retrieval; Demonstration Paper; Industry Paper.