The Hadron Collider Physics Symposia (HCP) are a new series of conferences that follow the merger of the Hadron Collider Conferences with the LHC Symposia series, with the goal of maximizing the shared experience of the Tevatron and LHC communities. This book gathers the proceedings of the first symposium, HCP2005 and reviews the state—of—the—art in the key physics directions of experimental hadron collider research: — QCD physics — precision electroweak physics — c—, b—, and t—quark physics — physics beyond the Standard Model — heavy ion physics The present volume will serve as a reference for everyone working in the field of accelerator—based high—energy physics.