An unpublished or unlisted phone number is a phone number which is not made publicly available in phone listings. As a general rule, customers must specifically request that their phone number not be published, and they may be required to pay a small fee. People who receive calls from an unpublished phone number can find out who owns the number, but it may take some work; several companies offer research services which include discovering the identity behind an unlisted phone number.

Most people get an unpublished phone number for privacy reasons. Many people who are prominent in the public eye prefer that their numbers not be listed to avoid harassment and frequent phone calls. Politicians and celebrities commonly have unlisted phone numbers so that they can remain unmolested at home. Others may be concerned about personal safety, choosing to leave their numbers unpublished to avoid stalkers or other unwanted attention.

The disadvantage to having an unpublished phone number, of course, is that it can be challenging for people to contact you. As a general rule, people who choose not to publish their numbers actively seek this, and they tend to guard the unpublished phone number closely, controlling access to it to ensure that it does not end up in the wrong hands. For example, politicians will print their office numbers on business cards and stationery, but not their home numbers, and people who have information about an unpublished phone number are usually sternly told not to pass it on.

There are more sinister reasons for having an unpublished phone number. People who use their phones to harass people may request unlisted phone numbers so that when their victims look the number up, they will not be able to figure out who owns it. Many companies also routinely use unpublished numbers to make it difficult for people to contact certain individuals within the company, which can be a source of frustration to consumers.

Some companies use unpublished phone numbers to provide special perks and services to clients. For example, some restaurants have a private reservation line at an unpublished phone number for very important patrons, ensuring that these patrons get prompt service and a reservation when they need it. Others use unpublished phone numbers to allow people to skip the queue of service personnel, getting immediate assistance with a problem or issue.

When an unpublished phone number is leaked, it can be both disastrous and irritating. Many websites are not afraid to publish private numbers when they are able to track them down, allowing people to do things like calling celebrities on their cell phones or to contact politicians at home. When someone has gone to the trouble of obtaining an unpublished phone number, the leaking of that number will usually cause them to abandon it and request a new phone number.