Castor oil was used as a medicine dating back to ancient Egyptian times. During the past centuries, castor oil has been employed in numerous modern applications. Castor oil contains an uncommon hydroxy fatty acid (HFA) at extremely high concentrations (90%). The hydroxy group imparts unique chemical and physical properties that make castor oil a vital raw material for manufacturing an increasing number of industrial products, such as high lubricity, long life lubricants and greases, a variety of polymers traditionally made by petroleum-based products for various coatings, elastomers and plastics, and an array of castor oil derivatives utilized in the cosmetic industry. Because of the high oil concentration in castor seeds (50% of dry seed weight), castor is also cultivated as a feedstock for biodiesel production. Due to the toxin ricin found in castor seeds, the US Department of Agriculture is developing a safe source of HFA, which is known as lesquerella. This book presents a wide range of research results on castor oil production and applications. State-of-the-art technologies have been employed to depicting molecular species and pathways involved in the bio-synthesis of castor and lesquerella oils. Novel applications of castor oil has been developed such as biodegradable nanocomposites to be used as superior wound dressing materials and new polymers for sustainable polyurethane foams. Up-to-date information on global castor crop production, oil processing and utilization has been extensively reviewed.