The concept of Open Science (OS) is being actively developed through the efforts of its key actors which constitute the OS information ecosystem. The purpose of the study is to substantiate the areas of research library activity within the open science information ecosystem taking into account the interaction with other actors. To achieve this goal, the following tasks are solved: 1) analysis of the interaction vectors of the main actors of the open science information ecosystem (scientific foundations, publishers, research libraries, scientific organizations), 2) identification of best practices (separate directions) of libraries on developing the open science information infrastructure, 3) determination of the development of research libraries as actors in the open science information ecosystem. Significant information and technological changes associated with the development of OS infrastructure have been identified. These changes are transforming information and research library services, impacting users’ information needs (open publications, compliance with publisher and research funder requirements for providing primary research data, etc.), and imposing new qualification requirements on library professionals. It is concluded that for research libraries, the development of the open science information ecosystem leads to not only an expansion of traditional library services but also the adoption of a range of new roles and functions: developing auxiliary models for research data management, creating information support services for open research, integrating library services into the research and educational process, promoting scientific results, etc. Based on an analysis of global practices in research library activities in the open science information ecosystem, directions for its development as an actor in the open science information ecosystem are identified and presented. Such a library, through active interaction with other actors and the required level of qualifications, is capable of effectively performing the functions assigned to it in accordance with the changing needs of users.
