First of all, the principle of fusion is briefly described together with materials requirements for fusion devices. These materials will have to function in extreme conditions, being subjected to complex thermal, mechanical and chemical loads as well as strong irradiation. As material properties change with these loads, various components may incur damage during service and the need for repairs without long shut-downs then add to the complexity of materials issues. As traditional construction materials are often at their limits, new materials are being sought, such as special composites, layered structures and coatings. The main coating applications proposed for fusion devices are reviewed including plasma facing components to protect the construction materials from particles and heat flux from the plasma, tritium barriers within the blanket system, electrically insulating coatings, corrosion barriers to permit higher temperature operation, etc. The required properties include thermal expansion match/bonding with substrates, acceptable neutronic properties, radiation damage resistance, safety/environmental characteristics to mention the major ones. The used technology should be economical, allowing coating large area components and/or complex shapes preferably in a single step, permitting in-situ repair of damaged parts and formation of graded composites with high coating thickness. Selected examples of applications are then presented.