The Relativistic Quantum Information (RQI) Action seeks to understand the relationship between Quantum Information Science (QIS) and the other major major paradigm of modern physics, namely, the theory of relativity. The latter describes physical processes as taking place in a spacetime that is subject to fundamental symmetries, and it also accounts for the description of gravitational phenomena. RQI will apply quantum information concepts to fundamental problems of relativistic physics, as they appear in diverse research fields, but it also aims to incorporate the fundamental principles of relativistic theories into the foundations of QIS, in order to create novel opportunities for theory and technological applications. The domain of the Action cuts across different research fields of the physical sciences, including quantum information science and technology, high-energy physics, quantum foundations, quantum gravity, mathematical physics, quantum optics, and space science. RQI will create a strong network that will bring together researchers from different disciplines, both theorists and experimentalists, to share their perspectives, in order to advance both fundamental physics and quantum technologies. The Action will develop a common conceptual framework that overcomes the limitations of existing specializations, it will promote visionary experiments to settle foundational issues in physics, it will work together with the industry and space agencies, and it will construct a roadmap for the longer-term development of the research field.