Funders increasingly mandate researchers to publish their scientific articles open access and to retain their copyright. Universities all over the world use repositories for the preservation and dissemination of academic production of their institutions, including scientific articles, datasets, and other research outputs. However, in general, authors do not find institutional repositories very attractive and accessible as an open access publication platform since repositories are not part of the rewarding system. We expect that researchers are more likely to publish and deposit their scientific papers in a repository, once they have the appearance, recognition and dissemination of a scientific journal. University libraries from five European countries started a collaboration to set up University Journals as an alternative to the current journal system that require authors to transfer their copyright, or charge article processing charges. If a scientific paper in a repository is submitted to and accepted by University Journals, the article will be automatically transformed into a publication in this newly accredited platform. By building on the existing repository infrastructure and publishing expertise of the participating universities, University Journals requires only modest resources, while the journal format will help ensure the commitment and acceptance by academic authors. University Journals will also stimulate Open Science practices. All research output (reports, datasets, tests, protocols, methods, software and other research products) can be published quickly and fully in University Journals. The advantage is that all types of publications will be indexed in the same way in established abstract and citation databases, by current search engines and copyright and ownership of all research outcomes will remain within the universities. And although University Journals is a single publication platform, it will be given the appearance of various digital journals, organized by discipline and university. It will provide a valuable way of modern scholarly communication as demanded in the transition to Open Science. In 2019, we received a starting grant to establish University Journals. Fourteen universities will collaboratively set up the publication and dissemination process. Publication will rely on internal quality control, while peer review will be voluntary, post hoc, open and transparent. Management and editorial tasks will be delegated to the libraries. A first (beta)version of the platform is scheduled to be online by June 2020. There is an open invitation for other universities to join the collaboration. The platform will co-exist with commercial journals, but academic and research libraries gain control of the publication and dissemination process on behalf of the authors and institutions. The costs of the common infrastructure can be shared among participating universities and possibly other stakeholders such as national funding agencies and governments. This paper will explain the University Journals project and how the involved universities want to facilitate a valuable alternative publication platform that complies with Plan S principles and enables publication and dissemination of all research outcomes. By establishing University Journals as a publication platform, university libraries are instrumental (and crucial) in achieving the ambitions of Open Science.