In the field of inventory management, a stock keeping unit (SKU ) is a distinct type of item for sale,: 122 such as a product or service, and all attributes associated with the item type that distinguish it from other item types. For a product, these attributes can include manufacturer, description, material, size, color, packaging, and warranty terms. When a business takes inventory of its stock, it counts the quantity it has of each SKU.

SKU can also refer to a unique identifier or code, sometimes represented via a barcode for scanning and tracking, that refers to the particular stock keeping unit. These identifiers are not regulated or standardized. When a company receives items from a vendor, it has a choice of maintaining the vendor's SKU or creating its own.: 74–75 This makes them distinct from Global Trade Item Number (GTIN), which are standard, global, tracking units. Universal Product Code (UPC), International Article Number (EAN), and Australian Product Number (APN) are special cases of GTINs.