Genetic diversity refers to the range of different inherited traits or the variation in the alleles and genotypes within a species. The genetic diversity of a particular habitat depends on factors such as the nature of the environment, which in turn consists of factors such as climate and the availability of food and other natural resources. Genetic diversity occurs due to three distinct causes, namely, mutation, recombination, and immigration of genes. It plays a crucial role in deciphering evolutionary and adaptive process for most species. It is also used to implement conservation strategies and crop management. Genetic diversity is gradually declining due to human activities. Around the world, forest habitats and wetlands are being altered, most of which are rich in flora and fauna species. Such lands are now being drained for agriculture and urban development. Humans are engaged in overfishing activities, which has led to the endangerment of many marine fish species and disruption of the ocean ecosystems. This book provides comprehensive insights on genetic diversity. A number of latest researches have been included to keep the readers up-to-date with the recent developments in the concerned area of study.