Every actor (human or machine) exploiting an EOSC Service. An EOSC System User might be further specialised in roles including (a) End-users, i.e. a Researchers, Research Administrator, and Third-party Service Provider, (b) a Supplier, i.e. EOSC Service Component Supplier, Data (Service) Supplier, EOSC Service Developer, (c) an EOSC System Manager, i.e. EOSC System Owner, EOSC System Top Manager, EOSC Service Provider.