A supplier, also known as a merchant or a vendor, is anyone who either manufactures or sells a product or service to a customer or third party for resale. A supplier may also be the third parties, who themselves sell their products or services to another business for resale.  A supplier can be the provider of the raw materials from the source, minerals, agricultural products, etc, but usually applies to a provider of a finished or processed product.

A supplier will be the first stage vendor of a product; a wholesaler or distributor will be a second stage merchant, selling numerous suppliers products to resellers, normally in a similar industry sector. Packagers of products who scale down large volumes of products to a saleable items are also suppliers and many of these allow for own label branding by smaller suppliers to sell as their own products.

Most suppliers will normally sell their products to a third party before the products reach the sale point to the consumer. Many larger suppliers do not sell direct to the consumers, but supply their products to importers, regional distributors, wholesalers, who then select the retailers and resellers for delivering the products to the consumers.