The main ingredient in whey protein powder is whey protein, which is a complete protein derived from milk. It typically contains all of the essential amino acids that the body needs to build and repair muscle. Other ingredients that may be included in whey protein powder include sweeteners, flavors, thickeners, and other ingredients that are used to improve the taste, texture, and nutritional profile of the powder. Some whey protein powders may also contain added vitamins, minerals, and other nutrients to support overall health and wellness. However, the exact ingredients in whey protein powder can vary depending on the brand and type of whey protein powder.