Alloys with high configurational entropy fundamentally differ from traditional alloys as they contain not one, but five or more basic elements with concentrations of 5 to 35 at.% each. Owing to the unique elemental composition, high-entropy alloys can have unusual functional properties such as high strength and wear resistance, exceptional heat resistance, good structural stability and good resistance to corrosion and oxidation. The review considers methods of synthesis of high-entropy alloys, methods and results of computer simulation of the high-entropy alloy structures and applications of such alloys as corrosion-, heat- and radiation-resistant materials and biomedical materials. Particular attention is paid to the prospects for the use of such alloys as protective coatings. The bibliography includes 352 references.