Areas weakly or not interconnected with large power grids, and in particular islands, usually rely on fossil energy sources for their electricity production. This results in high levels of emissions and pollution, but also higher costs than what can be found on the continents. In order to reduce their energy dependence while helping get closer to carbon neutrality, recourse to renewable energies is preferred. However, these need to be coupled with energy storage means to cope with their variability and their intermittence. If battery storage is often considered, hydrogen can have complementary contributions to that of batteries, especially in terms of long-term storage, integration between different sectors (electricity, transport and heat) or even the provision of ancillary services. However, the roles that hydrogen can play in the energy transition of islands are still insufficiently studied. The HyLES project aims to study the roles and impacts that hydrogen can have to support a transition to energy independence and carbon neutrality for electricity production and transport in weakly or non-interconnected areas. It will particularly focus on three case studies with different locations, needs, resources, economies and cultures: Corsica, Reunion Island and two islands in French Polynesia. As an interdisciplinary approach between engineering sciences, climate sciences and human and social sciences is particularly necessary on this subject, the project relies on contributions from partners (FEMTO-ST, GEPASUD, LE2P-ENERGY Lab and SPE) from these three fields and the three studied areas. First, the project will study local contexts not only in terms of production and consumption potentials, but also in terms of socio-economic barriers to the integration of hydrogen technologies. Studies by 2050 and beyond will make it possible to envisage different prospective scenarios taking into account the expected impacts of climate change. In a second step, these results will be used for integration at the local scale (building, district) and at the scale of the island networks. This integration will be based not only on electrical needs, but also on the decarbonization potential of transport (land and sea) or the production of hot and cold. Finally, in a last part, the project will carry out a study of the socio-economic impact of the integration of hydrogen technologies on the studied territories, and will publish a white paper of recommendations regarding the integration of hydrogen in island territories. Particular attention will be paid to interactions with the populations of the studied areas as well as with institutional, industrial and academic players.