Problem setting. In the countries of the European Research Area, the formation of public policies of Open Science is actively taking place. For Ukraine, the relevance of public open science policy is determined by Ukraine's involvement in the European Research Area which is impossible without synchronizing the formation of new and adaptation of existing public policies, including in the field of science. This causes the need for research in the field of open science, and in particular the existing practices of formation and implementation of relevant public policies in the European and world research areas.Recent research and publications analysis. General issues of open science and open data are often considered in the publications of such Ukrainian and foreign scientists as T. Yaroshenko, I. Kuchma, O. Chmyr, Mirowski P. and others. At the same time, it should be noted that the issue of public policy of open science is rarely considered by Ukrainian scientists.The paper objective is theoretical substantiation of conceptual bases of establishment and realization of the public open science policy.The paper main body. The article considers the establishment of the open science paradigm as the initial stage of formation of the relevant policy. The role and place of such a civil society institution as professional associations in this process is demonstrated. The analysis of three main open science documents— Declaration of Budapest Open Access Initiative, Bethesda Statement on Open Access Publishing and Berlin Declaration on Open Access to Knowledge in the Sciences and Humanities — was carried out. The existing problems on the way to ensuring openness in the scientific sphere are considered, as well as possible ways to solve them. The role of the Internet and one of the types of e-infrastructures, namely repositories, in the actual implementation of open science policy is noted.Conclusions of the research. In the formation of the paradigm of open science and, as a consequence, the policy of open science at the national and international levels, a key role was played by such an institution of civil society as professional associations. It was the efforts of professional activists (scientists, publishers, librarians, grant providers, employees of higher education institutions, etc.) for the first time formulated the basic definitions of open science and open access as part of it, outlined areas of action and examples of necessary measures new knowledge. Such dissemination of knowledge cannot be considered effective if the information does not become widely and permanently available to all stakeholders.Given that research is an interdependent process in which new work is largely based on the results of previous scientific advances, the first documents relating to open science addressed first the issue of access to academic texts and scientific data, and the second - to cultural heritage sites, etc. The issue of access to the means of obtaining a scientific result (for example, to research infrastructures) at the initial stage of formation of the paradigm of open science was not considered. In addition, the issue of openness of science can be considered both universal (BIVD Declaration, Berlin Declaration) and professional (Bethesda statement, which emphasized the biomedical field of research).The driving force for the emergence and evolution of the paradigm of open science was the development of total internetization in the early 2000s, which allowed to obtain any information, including scientific, from anywhere on the planet under two conditions: access to the Internet and the absence of artificial barriers to accessing the information itself.The main obstacles in the way, according to the three documents discussed above, are financial (compensation for publishers who switch to open access, which mainly fell on the shoulders of the authors of publications), legal (copyright) and technical (network access). Internet and the availability of online repositories with unified algorithms). Accordingly, the way out of the situation is to provide reasonable benefits and funds for the publication of academic texts and research data in open access to research estimates, references to copyright only to ensure proper recognition, and the creation of an appropriate system of online repositories and public access. to the Internet.An essential common feature of the three documents discussed above is the emphasis on the need to consider and take into account the content and substantive contribution of the published academic text, rather than the prestige or reputation of the publication in which it is published, when evaluating a scientist or considering his candidacy. promotion. In addition, it is important to treat the publication of works in open access as proof of community service (by analogy with the attitude to volunteering in other areas of life).Activists who laid the foundations of the open science paradigm relied primarily not on the centralized formulation and implementation of relevant policies (as was the case in 2010), but on educational activities among stakeholders on the benefits of publishing their research results in open access.