Abstract: Inventories of open science initiatives differ in scope, geographic coverage and classification, making it difficult to compare infrastructures, services, networks and policies. We developed COSMI Hub within the OPENIT project to bring these sources together in a curated dataset. The release archived on 8 October 2026 contains 1,186 records and 71 variables covering initiative identity, source provenance, geography, record level, operational status, thematic activities, governance, funding and external identifiers. We identified candidates through structured directories, policy documents, official websites and suggestions from the open science community, then checked identities, reconciled duplicates and assessed supporting evidence. The dataset distinguishes standalone initiatives, services, deployments, umbrella organisations and policy instruments. Records can be assigned several thematic dimensions, with uncertainty retained where evidence is incomplete. We describe the collection and coding methods, the data structure and file-level checks, together with considerations for reuse. The Zenodo release is fixed, whereas the companion dashboard is updated separately. Because we assembled the collection purposively, it cannot be used to estimate the worldwide number of open science initiatives.