The 3rd European Workshop on Maritime Systems Resilience and Security (MARESEC) was dedicated to the research on Resilience, Security, Technology and related Ethical, Legal, and Social Aspects (ELSA) in the context of Maritime Systems, including but not restricted to Offshore/Onshore Infrastructures, Navigation and Shipping and Autonomous Systems. The event, organized by the Institute for the Protection of Maritime Infrastructures of the German Aerospace Center (DLR), took place virtually on June 27th , 2023, with over 60 participants. Out of all submitted extended abstracts, 13 were selected for oral presentations, and 2 keynotes were delivered on Maritime Surveillance and Networked Autonomous Underwater Robots. Additionally, 2 student presentations were held. The contributions to the conference came from institutions in 22 countries. The final schedule can be found in the appendix.