Postal services, also called mail services, are the procedures involved in the collection, handling, and delivery of letters, messages, and packages. Post offices are places where mail is handled and postal materials and services are sold. The terms postal service and post office can also refer to a government agency that provides mail services. In the United States, the government agency that provides mail services is called the United States Postal Service. In the United Kingdom, it is called the Post Office. India Post provides similar services in India, as does An Post in Ireland. In Australia, the postal service is the Australian Postal Corporation, which operates under the name Australia Post; in Canada, it is the Canada Post Corporation, or Canada Post.

Mail is perhaps the one service of central government that touches nearly every citizen on almost a daily basis. Indeed, in many small towns, the post office is the only government building. By means of letters, people can share news and make plans with friends and relatives far away. Businesses send bills and receive payments through the mail. Most magazines and mail-order catalogs are delivered by mail.

Postal services have played a major role in the building of nations and the uniting of people throughout history. In ancient times, an extensive system of messenger routes served to knit the Roman Empire together. In Australia, Canada, and the United States, the postal services helped promote democracy by uniting citizens who were scattered over a vast continent. Until well into the 1900's, the postal services were the primary vehicle for communication and marketing.

The postal industry is big business. Postal agencies are large organizations, traditionally government-run, with many complicated managerial and economic concerns. The United States Postal Service, for example, is the country's largest single employer of civilian labor, with about 900,000 full- and part-time employees. About 80 percent of the costs of postal administration consist of payrolls and other labor expenses.

Mail service has long ranked as a vital public service, as well as a source of revenue for the government. Postal systems traditionally have an obligation of universal postal service