Mail order is a term which describes the buying of goods or services by mail delivery. The buyer places an order for the desired products with the merchant through some remote method such as through a telephone call or web site. Then, the products are delivered to the customer. The products are typically delivered directly to an address supplied by the customer, such as a home address, but occasionally the orders are delivered to a nearby retail location for the customer to pick up. Some merchants also allow the goods to be shipped directly to a third party consumer, which is an effective way to send a gift to an out-of-town recipient.

A mail-order catalog is a publication containing a list of general merchandise from a company. Companies who publish and operate mail-order catalogs are referred to as catalogers within the industry. Catalogers buy or manufacture goods then market those goods to prospects (prospective customers). Many catalogers, just as with most retailers, are increasingly buying goods from China. Catalogers "rent" names from list brokers or cooperative databases. The catalog itself is published in a similar fashion as any magazine publication and distributed through a variety of means, usually via a postal service and the internet.

Sometimes supermarket products do mail-order promotions where people can send in the UPC code plus shipping and handling to get a product made especially for the company.

Few things are not available through mail order.