This two-volume set CCIS 3091-3092 constitutes the proceedings of the 13th Multidisciplinary International Social Networks Conference, MISNC 2026, held in Danang, Vietnam, during August 10–12, 2026.The 79 full papers included in these volumes were carefully reviewed and selected from 166 submissions. They are organized into the following topical sections:Part I: Multidisciplinary Social Networks Research; Digital Technologies and Social Networks in Cultural Heritage Preservation; Human–AI Collective Intelligence and Collaborative Decision SystemsPart II: Network, Economic and Business Studies; The Use of AI in Social Media and Daily Life; and AI-Driven Applications in Business and Society