This volume constitutes the refereed proceedings of 9th International Workshop on Annotation of Real-World Data for Artificial Intelligence Systems, ARDUOUS 2025, held in Bologna, Italy, during October 25–26, 2025.The 11 full papers included in this book were carefully reviewed and selected from 16 submissions. These papers have been categorized into the following themes: Automating Ergonomics: Scalable AI for Technical Hand Grip Classification; Activity Recognition; Annotation of Textual Data; Relation Extraction from Real-World Unstructured Text in the Domain of Dementia.