A DUNS number is a unique nine-digit identifier assigned to a single business entity by Dun & Bradstreet (D&B) through the Data Universal Numbering System (DUNS) . It was introduced in 1963 to support D&Bs credit reporting practice and is standard worldwide. The DUNS number is a random nine-digit number that has no apparent significance and is assigned to each business location in the D&B database, having a unique, separate, and distinct operation for the purpose of identifying them. The DUNS database contains over 300 million entries for businesses throughout the world.

The DUNS number is used by many organizations, including the European Commission, the United Nations, the United States government, and Apple. More than 50 global industry and trade associations recognize, recommend, or require DUNS. Many businesses use the DUNS number to access a companys Dun & Bradstreet credit profile to help evaluate them as a partner.

A DUNS number is sometimes formatted with embedded dashes to promote readability, such as "15-048-3782". Modern usage typically omits dashes and shows the number as in the form "150483782". Businesses may choose to append four extra alphanumeric characters to their DUNS number, called a DUNS+4 number.

A DUNS number is required for businesses that contract with government agencies. It is also useful for businesses that are planning to seek financing or grow their business to make it easy for lenders to understand a business’ credit history. There is no downside to creating a DUNS number and maintaining a basic credit profile, even if a business does not plan to contract with government agencies or seek financing.