This comprehensive volume presents the fascinating and diverse world of microbial secondary metabolites, exploring their biosynthesis, ecological roles, and wide-ranging applications in biotechnology, pharmacy, agriculture, and various other industries. The initial chapters provide a foundational overview of microbial secondary metabolites and their immense value. The subsequent chapters discuss microbial strain engineering, enzymatic pathways, and metagenomic approaches to unlock hidden biosynthetic potential. Emphasis has also been given to how these natural products contribute to sustainable development, including eco-friendly agricultural practices and stress alleviation in crops through plant–microbe interactions. The book further explores source-specific contributions, with dedicated chapters on bacterial, fungal, algal, and marine microbial metabolites. Innovative applications are also highlighted in various chapters with recent advancements in technologies such as microbial mycoherbicides for weed control, viral-derived metabolites, and the promise of marine microbial communities. Special attention has also been given to sustainable exploitation and the integration of these compounds into functional products and solutions for global challenges. This book serves as a valuable reference for researchers and students of microbiology, biotechnology, and environmental sciences. The editors would welcome the fruitful suggestions from the readers to be incorporated into future editions.