Microbial ecotoxicology is a multidisciplinary field that explores the interactions between microorganisms and environmental pollutants, explaining their impact on ecosystems and human health. At its core, microbial ecotoxicology explores how pollutants alter microbial communities, microbial functions, and biogeochemical cycles in various environments, from soil and water to air and sediments. Sub-disciplines within this field involve microbial diversity and community dynamics, microbial metabolism and biodegradation pathways, and the ecophysiology of pollutant-tolerant microorganisms. The current applications of microbial ecotoxicology are far-reaching. They include environmental monitoring and risk assessment, where microbial indicators serve as early warning signals of ecosystem perturbations and pollution events. Additionally, microbial bioremediation technologies offer sustainable solutions for the cleanup of contaminated sites. This book provides comprehensive insights into the field of microbial ecotoxicology. The book presents researches and studies performed by experts across the globe. It will help the readers in keeping pace with the rapid changes in this field.