This review paper examines the core technologies and their technical and life cycle analyses of energy storage systems (ESSs) in non-interconnected European islands. The need for ESSs is highlighted due to the challenges posed by stochastic renewable energy sources (RES) in these systems, such as photovoltaics (PV) and wind farms (WFs). The paper provides an overview of the current status of storage solutions, including electrochemical, mechanical, and thermal ESSs, and discusses their ancillary services, particularly in non-interconnected islands. Key technologies like batteries, hydro-pumped storage, flywheels, and fuel cells are analyzed, with a focus on their energy density, efficiency, and lifespan. The paper also details existing installations in non-interconnected European islands, such as Ikaria, Agios Efstratios, Tilos, Kythnos, Terceira, Madeira, Porto Santo, Faroe Islands, Favignana, Ustica, El Hierro, Gran Canaria, Eigg, and Marie-Galante. The most popular ESS solutions are lithium-ion batteries and hydro-pumped storage, often combined with other technologies. The paper concludes by discussing future trends and challenges, noting that by 2030, Europe is expected to have nearly 12 GW of ESSs, with Greece leading in terms of non-interconnected islands.This review paper examines the core technologies and their technical and life cycle analyses of energy storage systems (ESSs) in non-interconnected European islands. The need for ESSs is highlighted due to the challenges posed by stochastic renewable energy sources (RES) in these systems, such as photovoltaics (PV) and wind farms (WFs). The paper provides an overview of the current status of storage solutions, including electrochemical, mechanical, and thermal ESSs, and discusses their ancillary services, particularly in non-interconnected islands. Key technologies like batteries, hydro-pumped storage, flywheels, and fuel cells are analyzed, with a focus on their energy density, efficiency, and lifespan. The paper also details existing installations in non-interconnected European islands, such as Ikaria, Agios Efstratios, Tilos, Kythnos, Terceira, Madeira, Porto Santo, Faroe Islands, Favignana, Ustica, El Hierro, Gran Canaria, Eigg, and Marie-Galante. The most popular ESS solutions are lithium-ion batteries and hydro-pumped storage, often combined with other technologies. The paper concludes by discussing future trends and challenges, noting that by 2030, Europe is expected to have nearly 12 GW of ESSs, with Greece leading in terms of non-interconnected islands.