While most papers on high-entropy alloys (HEAs) focus on the microstructure and mechanical properties for structural materials applications, there has been growing interest in developing high-entropy functional materials. This presentation will provide a brief, timely review on select functional properties of HEAs, including soft magnetic, magnetocaloric, physical, thermoelectric, superconducting, hydrogen storage, catalyst, and (anti-wear, bond, thermal barrier) coatings. Comparisons of functional properties between HEAs and conventional low- and medium-entropy materials will be provided. Extending the HEA concept to a wide range of materials such as intermetallics, ceramics (oxides, carbides, nitrides, borides), and semiconductors through the iso-structural design approach will be discussed. Perspectives will be offered in designing high-performance high-entropy functional materials integrating high-throughput experiments and computational modeling. For example, charge neutrality consideration and integrating defect chemistry and CALPHAD will be illustrated for designing high-entropy cathode materials in the example of classic perovskite LaMnO3±δ for solid oxide fuel cell applications.