Abstract: Open Research (OR) and Open Science (OS) have become central to efforts to improve the transparency, accessibility, and reproducibility of research, while reforming Researcher Assessment (RA) toward more responsible approaches that value a broader range of contributions beyond publication-based metrics. This global landscape review maps how OR-related documents, resources, and initiatives have evolved and how they intersect with Responsible Researcher Assessment (RRA), with particular attention to the role of Research Performing Organisations (RPOs) as key implementers of policy and culture change. Using a multi-method search strategy across web search engines, databases, internal project knowledge, and citation-chaining, the authors compiled and coded a dataset of 100 English-accessible, transdisciplinary OR resources published between 31 January 2012 and 31 July 2025. Each resource was categorised by type, topic, intended audience, publication year, and three geographical dimensions (production level, author provenance, and audience reach), and analysed using Excel and Power BI (For the dataset see HERE). Findings show a sustained rise in OR documentation over the past 13 years, with a marked acceleration from 2020 to 2023 and peak output in 2021–2022, suggesting increased attention to openness and collaboration during and after the COVID-19 period. Regional production dominates (57%), particularly within Europe, while most resources are written for a global audience (71%), indicating a globalising orientation even when initiatives originate nationally or regionally. Seventeen resource types were identified, with reports and toolkits most prevalent (32% combined), reflecting both strategic guidance and practical implementation support. Topic analysis identified 25 themes, dominated by Responsible Research Assessment (58%) and Open Science/FAIR Data (44%), alongside recurring concerns about metrics, incentives, and reward structures. RPOs were the most frequently addressed audience, followed by funders and researchers, underscoring the institutional locus of change. Key limitations include English-language bias and the exclusion of discipline-specific and less findable resources. Overall, the review evidences a maturing OR ecosystem increasingly shaped by regional collaboration and global dissemination, with assessment reform and data openness as persistent drivers of change.