Making the resources produced by researchers fully reusable and understood requires specific efforts. The Findable, Accessible, Interoperable and Reusable (FAIR) principles were elaborated to address these issues, describing a set of requirements for resource reusability and interoperability. These principles have been gaining increasing attention in a range of different areas and applications. One the one hand, a key aspect is the ability of properly and semantically describing resources, in particular with the help of ontologies. On the other hand, ontologies themselves have to be compliant with the FAIR principles. This series of workshops has the following goals: (a) to bring together leaders from academia, industry and user institutions to discuss the adoption of FAIR principles in real-world requirements. (b) to serve to inform industry and user representatives about existing research efforts that may meet their requirements. (c) to investigate how the FAIR principles are supported by the use of schemes, vocabulaires, and ontologies that ideally are themselves FAIR. In 2023, we have a twin workshop at both FOIS and SEMANTICS conferences. The primary aim is to bring the gap between the scientific and the practitioner/industry sides, respectively, where we would take the greatest and latest advances in the state of the art to industry and bring back the practitioners’ needs and challenges to the scientific community of figure out a solution. This proceedings brings together works presented at both editions: 3rd edition at SEMANTICS and 2nd edition at FOIS. Both editions received 3 submissions where 2 of them have been accepted. For Onto4FAIR@FOIS, one of the papers has been accepted only for presentation following the reviewers recommendation and has not been included in the proceedings. Each submission were reviewed by three collaborators from our program committee. Our sincere thanks to the members of the Program Committee and all the authors who submitted their work and participated in the event. Both workshops also counted with an invited talk entitled A FAIR Catalog of Ontology-Driven Conceptual Models by Tiago Sales at FOIS and Claudenir M. Fonseca at SEMANTICS, both researchers at Semantics, Cybersecurity and Services (SCS), University of Twente, Enschede, The Netherlands, involved in the FAIR catalog projet. We warmly thank the speakers for their presentations.