Plant development and productivity are negatively regulated by various environmental stresses. Abiotic stress factors such as heat, cold, drought, salinity, wounding, heavy metals toxicity, excess light, flooding, high speed wind, nutrient loss, anaerobic conditions and radiations etc. represent key elements limiting agricultural productivity worldwide. The loss of productivity is triggered by a series of morphological, physiological, biochemical and molecular stress-induced changes. Such an unfavorable situation is in contrast with the increasing global food demand. . Global climatic pattern is becoming more unpredictable with increased occurrence of drought, flood, storm, heat waves, and sea water intrusion. It has been estimated that abiotic stresses are the principal cause for decreasing the average yield of major crops by more than 50 %, which causes losses worth hundreds of millions of dollars each year. Therefore, to feed the world population maintaining crop productivity even under unfavorable environment is a major area of concern for all nations. Developing crop plants with ability to tolerate abiotic stresses is need of the day which demands modern novel strategies for thorough understanding of plant's response to abiotic stresses. In this book we present a collection of chapters that are deals in the field of plant abiotic stress tolerance and crop improvement. The chapters provide a state-of-the-art account of the information available on abiotic stress tolerance and crop improvement.