Reliable and stable operation under pressure is one of the major challenges of currently existing Solid Oxide Electrolysis (SOEL) technologies for its ultimate application in relevant sectors such as energy storage and transport. The main goal of HyP3D is to overcome this barrier by delivering disruptive ultra-compact and lightweight high-pressure SOEL stacks, able to convert electricity into compressed hydrogen, for gas grid injection (P2G) and on-site generation in Hydrogen Refueling Stations (HRS). HyP3D stacks are based on innovative 3D-printed SOEL cells with unprecedented mechanical properties, embedded functionality and self-tightening capabilities implemented by design. These unique advantages will allow operation at pressures above five bars without the need of unpractical, energy inefficient and costly pressure vessels, which is the only actual solution for pressurization despite their low reliability. Breakthrough HyP3D geometries will multiply by more than three times the volume and mass specific power density of conventional technologies (reaching 3.40kW/L and 1.10 kW/kg, respectively), resulting in pressurized SOEC stacks with a remarkably reduced footprint (one third of state-of-the-art stacks) and ultra-low use of raw materials (76% reduction). Moreover, the elimination of any vessel will increase the system efficiency, reduce the final cost and substantially simplify the scaling-up towards required MW-size systems. The project is product-driven and involves industrial partners with proved experience in mass manufacturing of ceramics by 3D printing, glass-to-metal sealing and assembly of electrolysers, which will ensure, together with the presence of P2G and HRS stakeholders, competently covering the entire value-chain. HyP3D technology will be fabricated in a pilot line, which will ensure reaching stack level and validation at laboratory scale by 2025 (TRL=4).