A postcard or post card is a rectangular piece of thick paper or thin cardboard intended for writing and mailing without an envelope. Shapes other than rectangular may also be used. There are novelty exceptions, such as wood postcards, made of thin wood, and copper postcards sold in the Copper Country of the U.S. state of Michigan, and coconut "postcards" from tropical islands.
In some places, one can send a postcard for a lower fee than for a letter. Stamp collectors distinguish between postcards (which require a stamp) and postal cards (which have the postage pre-printed on them). While a postcard is usually printed by a private company, individual or organization, a postal card is issued by the relevant postal authority.
The world's oldest postcard was sent in 1840 to the writer Theodore Hook from Fulham in London, England. The study and collecting of postcards is termed deltiology.