A sweetener is a molecule that gives a food, or a drink, a sweet taste, thus activating the areas of taste used to perceive this as flavor. Sweeteners, as they increase the palatability of food, are widely used in the production, including industrial, of foodstuffs. In this regard, it is a common practice to add quantities of sugar to the recipes in order to gain consensus on the food market, since the sweetest products are most welcome among consumers. The need to use sweeteners has increased significantly in recent decades, due to the increased sensitivity to problems caused by excess sucrose (the common kitchen sugar) in human nutrition. It is clear that a diet rich in sugars, which exceeds 5% of daily caloric needs, can lead to very important pathologies ranging from common caries to diabetes. For this reason, it is preferred to adopt different “safer” solutions. In this chapter, the most commonly used sweeteners have been described, highlighting their chemical structure, their safe amount, and utilizable and toxic effects, where applicable. To guarantee an easy reading, the chapter includes three categories, natural sweeteners, sugar alcohols and intense sweeteners, which collect all the similar sweeteners.