This book constitutes the refereed proceedings of the 19th International Conference on Similarity Search and Applications, SISAP 2026, held in Brno, Czech Republic, during October 14–16, 2026.

The 12 full papers and 12 short papers included in the proceedings were carefully reviewed and selected from 60 submissions. The book also contains 3 Doctoral Symposium papers, 1 Demonstration paper, and 13 SISAP Indexing Challenge papers. 

The contributions were organized in the following topical sections: Graph-Based Similarity Search; Indexing, Hashing and Sketches; Theory and Principles of Similarity Search; Clustering and Anomaly Detection; Sequence Search and Reranking; Search Parametrization and Personalization; Doctoral Symposium; and Indexing Challenge.