The goal of Heavy Ion Therapy Research Integration plus (HITRIplus) is to integrate and propel biophysics and medical research on cancer treatment with heavy ions beams while jointly developing its sophisticated instruments. Cancer is a central health problem for our society. Heavy ion beams irradiate tumours by focussing on the ill tissue while sparing the healthy part around, more effectively than any other irradiation treatment. The wider objective of HITRIplus is to provide radiation oncologists with a cutting-edge tool to treat the fraction of tumours that are not curable with X-rays or protons or have better survival rates or lower recurrences with ions. For this major initiative, HITRIplus has gathered a consortium engaging all relevant stakeholders and for the first time bringing together all four European ion therapy centres with leading EU industries, academia, and research laboratories. They all share the ambition to jointly build a strong pan-European Heavy Ion Therapy Research Community. A strategic partner is the South East European International Institute for Sustainable Technologies, which federates eight countries in South East Europe with the ambition to build a next generation heavy ion Research Infrastructure in the area, to boost research and cooperation in a region trying to rebuild after a troubled past. HITRIplus Transnational Access will integrate and open to external researchers the experimental programme of the five European facilities providing therapeutic ion beams. Its Networks will structure and foster the research on heavy ion therapy, including clinical and pre-clinical research. Joint Research Activities will develop new accelerator and beam delivery technologies to extend the reach of the present generation centres and to define a new European reference design, at lower cost and dimensions, to make cancer ion therapy more accessible and to open new markets to European industry.