This deliverable, D4.1 “Stakeholder Engagement Plan” describes the main objectives, strategy and expected outcomes of the Stakeholder engagement activities to be adopted over the lifetime of the HSbooster.eu project to ensure the successful achievement of the Project objectives and an effective outreach and participation of all the targeted Stakeholders. The plan is a living document, which can be subject to small changes, to address any specific needs or new opportunities that may arise during its execution or the necessity to focus the effort on a specific Stakeholder, or new ones arising during the 24 months of the initiative. The HSbooster.eu engagement strategy will adopt a pragmatic, holistic, and interconnected approach to successfully promote the project’s Open Call for Experts and Open Calls for R&I projects, as well as to disseminate their outcomes using an extensive set of communication channels to target the broad and diverse network of Stakeholders involved. This deliverable defines the different types of stakeholders identified, the engagement strategy devised to address each of them, the corresponding KPIs, the status of the current community (at the moment of writing) and the modus operandi and tools to be adopted. Additional information on communication activities and key events to facilitate outreach to the targeted communities will be provided in D5.1 (expected to be issued in M6).