Preface

Abstract

The 17th edition of the International Conference on Topics in Astroparticle and Underground Physics (TAUP 2021) was held from August 26 through September 3, 2021. For the first time in the TAUP series, started in 1989, the conference was organized as a fully online event due to the COVID-19 pandemic and hosted by IFIC Valencia, in collaboration with other Spanish institutions. IFIC (Instituto de Física Corpuscular) is a joint research institute belonging to two institutions: the Spanish National Research Council (CSIC) and the University of Valencia.The biennial TAUP series covers recent experimental and theoretical developments in astroparticle physics. The topics discussed at the conference included Cosmology, Dark Matter, Neutrino Physics and Astrophysics, Gravitational Waves, Outreach and Education, Underground Laboratories, High-Energy Astrophysics, Cosmic Rays and Multi-messenger Astronomy, as well as the intersection of these fields.The scientific program of this fully online TAUP event consisted of invited plenary talks, contributed talks and posters, as follows- Plenary sessions: invited talks and other live activities in the morning/afternoon/evening in American/European/Asian time.- Parallel sessions: asynchronous talks selected by the session conveners, pre-recorded and available for all registered participants before the conference started. Further discussion with the speakers was possible at live topical panels. A few of these talks were selected for live Hot Topic sessions.- A virtual poster session held on an interactive platform.List of Scientific Committees, TAUP 2021 International Advisory Committee, TAUP Conferences Steering Committee, TAUP 2021 Parallel Sessions and Conveners, TAUP 2021 Program at a glance, Plenary sessions, Parallel sessions: Hot Topics, Parallel sessions: Discussion panels, List of posters are available in the pdf.