In telephony, a telephone directory is a listing of telephone subscribers in a geographical area or subscribers to services provided by the organisation that publishes the directory. Subscriber names are generally listed in alphabetical order, together with their postal or street address and telephone number. It can be published in hard copy or in electronic form.
In the U.S., courts have ruled (in Feist v. Rural) that telephone companies do not have a copyright on telephone listings, which has meant availability of innovative telephone directory services on CD-ROM and the World Wide Web.
A telephone directory may also provide instructions about how to use the telephone service in the local area, may give important numbers for emergency services, utilities, hospitals, doctors, and organisations who can provide support in times of personal crisis. It may also have civil defence or emergency management information as well as advertising.
A telephone directory may also be called a phone book or may be known by the colour of the paper it is printed on.
They are not well known to the general public since they have generally been available on a limited basis to telephone companies or government officials, although genealogists and private investigators know which public libraries have them in their collection. In addition, some telephone companies have made the information generally available through little known services, such as the "2080 service" in Chicago (now discontinued), where a call to the exchange and the number 2080 produced an operator who would give the name and address of any other number in that exchange.