**1. Introduction**

The concept of high-entropy alloy (HEA), an alloy with five or more constituents with a concentration between 5 and 35%, has triggered extensive research to develop new metallic and ceramic high-entropy materials. Like HEAs, high-entropy ceramics (HECs) consist of multicomponent ceramic oxides, borides, and nitrides. The HECs exhibit homogeneous crystalline single-phase despite the complex structure of ceramic compounds and offer superior properties over the constituents and conventional ceramics. The development of high-entropy ceramic coatings is an important route to design new and novel high-entropy ceramic materials with superior properties for practical applications. In this chapter, the recent work on HECs is summarized in the following two sections: bulk HECs and HEC coatings. Bulk HEC section is focused on the processing and the evolution of significantly enhanced mechanical properties of borides, oxides, and carbide ceramics and composites. Moreover, the potential of HECs in thermal-electrical, tribological, and high temperature applications are discussed. In the section on high-entropy coatings, recently reported researches on different HEC coating techniques and the properties of the HEC coatings have been summarized.
