Thermonuclear fusion is a potential source of cleaner and safer energy for the future. Its technological realization depends on the development of materials able to survive and function in extreme conditions, often involving a variety of loading – thermal, mechanical, chemical and irradiation. Single bulk materials are often at the edge of their properties limits; therefore, composites and coatings are intensely studied. This article reviews the development, characteristics and applications of coatings for fusion reactor materials. First, the technological objectives and material-environment interactions are briefly summarized, together with materials requirements and the role of coatings. Then, specific applications in different areas of a fusion device are reviewed, namely the plasma facing components, electrical insulation, diffusion and permeation barriers. Various coating fabrication methods are mentioned and the respective coating characteristics are compared. Selected case studies are presented, with particular focus given to ITER and to ceramic coatings.