This book constitutes the refereed proceedings of the 20th EAI International Conference on Body Area Networks, BODYNETS 2025, held in Okayama, Japan, during December 2–4, 2025.The 40 full papers included in this volume were carefully reviewed and selected from 97 submissions. They are organized into the following topical sections: THz Sensing and Tissue Characterization; Sensing, Localization, and Motion Analysis in Body Area Networks; Physical-Layer Techniques for Medical and Body-Centric Systems; Advanced Sensing and Signal Processing for Health Monitoring; Clinical, Implantable, and Wearable Systems for Healthcare Applications; Molecular Communication and Bio-Inspired Networking Models; Body Area Networks and Wearable Systems for Reliable Health Monitoring; Reliable and Interference-Resilient Wireless Networks for Healthcare; and Human-Centric Sensing, Haptics, and Data Standardization.