Stressful environments such as drought, salinity, and high temperature (heat) cause alterations in a wide range of physiological, biochemical, and molecular processes in plants. These changes, compounded by climate change, threaten the sustainability of crops and challenge their growth and production. Drought or water stress is considered one of the most serious problems, which drastically affects the growth and physiology of corn (Zea mays L.) as well as many other crops. Understanding corn’s response to water stress at different levels will help to take the right actions and the appropriate strategies to limit the negative impact of water stress. Corn requires adequate amounts of water during all growth stages to achieve optimum growth and high yield. It is therefore important to match the water needs for each specific growth stage and avoid water stress during the sensitive growth periods of the growing season. In this chapter, we will focus on water stress and its effects on the growth and physiology of corn.