High-entropy alloys (HEAs) represent a groundbreaking class of materials with exceptional mechanical, thermal, and chemical properties, making them prime candidates for a wide range of advanced applications. This book explores the latest developments in HEA design, focusing on composition, microstructure, and their influence on material performance. From the use of machine learning in optimizing alloy properties to the application of molecular dynamics simulations in understanding phase transitions, this book covers a broad spectrum of approaches that enhance the design and application of HEAs. Additionally, exploring HEAs in catalysis and superconductivity provides valuable insights into their versatility across diverse fields. With comprehensive discussions on innovative design strategies, characterization techniques, and computational modeling, this book is an essential resource for researchers and professionals seeking to push the boundaries of material science. By offering a systematic approach to HEA composition and structure-property relationships, it equips readers with the knowledge to design high-performance alloys for future technological advancements.