A design of the research-demo High-Temperature Gas-cooled Reactor (HTGR) based on Japanese High Temperature Engineering Test Reactor (HTTR) technology that is updated and adjusted to Polish market requirements is presented. It is a collaborative design project of the National Centre for Nuclear Research (NCBJ) in Poland and of the Japan Atomic Energy Agency in Japan and is going to be built at the site of NCBJ near to the existing research light water reactor MARIA. The reactor thermal power is 30 MW, and it carries the name High-Temperature Gas-cooled Reactor—POLish Atomic (HTGR-POLA). The main objective of the design is focused on applications of high-temperature steam acting continuously in polygeneration. Steam temperature of 540°C, electricity, and district heat as well as perspectival hydrogen production are considered. The reactor’s core is prismatic (hexagonal graphite blocks), helium cooled, and TRISO fueled and possesses many inherent safety features. The current status of the project is basic design and large pieces of the Preliminary Safety Analyses Report finalized, ready to start detailed design and licensing.