The future Quantum Internet will provide radically new internet applications by enabling quantum communication between any two points on Earth. The Quantum Internet Alliance (QIA) targets a Blueprint for a pan-European Quantum Internet by ground-breaking technological advances, culminating in the first experimental demonstration of a fully integrated network stack running on a multi-node quantum network. QIA will push the frontier of technology in both end nodes (trapped ion qubits, diamond NV qubits, neutral atom qubits) and quantum repeaters (rare-earth-based memories, atomic gases, quantum dots) and demonstrate the first integration of both subsystems. We will achieve entanglement and teleportation across three and four remote quantum network nodes, thereby making the leap from simple point-to-point connections to the first multi-node networks. We will demonstrate the key enabling capabilities for memory-based quantum repeaters, resulting in proof-of-principle demonstrations of elementary long-distance repeater links in the real-world, including the longest such link worldwide. Hand in hand with hardware development, we will realize a software stack that will provide fast, reactive control and allow arbitrary high-level applications to be realized in platform-independent software. QIA's industry partners examine real world use cases of application protocols and their hardware requirements. We will validate the full stack on a small Quantum Internet by performing an elementary secure delegated quantum computation in the cloud. We will validate the design of the Blueprint architecture by a large-scale simulation of a pan-European Quantum Internet using real world fibre data. Through synergy of leading industrial, academic and RTO partners, QIA's Blueprint will provide a targeted roadmap for the main Flagship phase and set the stage for a world-leading European Quantum Internet industry.