Pen pals (or penpals) are people who regularly write each other, in particular in the case of snail mail. A penpal relationship is often used to practice writing and reading in a foreign language, improving literacy, to learn more about other countries and life-styles, and just to reach out and communicate with a fellow human being. Some people remain penpals for only a short time, while others continue to exchange letters and presents life-long. Some penpals eventually arrange to meet in 'real-life'. Penpals come in all ages, nationalities and cultures. Being part of a penpal network can be a way to gain a valuable understanding of the world, and an appreciation for cultures and lifestyles very different to your own.

Many people writing to a penpal are not using their native language in their letters.

A modern variation on the traditional penpal arrangement is to have a keypal and exchange email addresses as well as or instead of paper letters. This has the advantage of saving money, but also the disadvantage that the communication is very ephemeral. Many people prefer to receive paper letters, gaining the satisfaction of seeing their name carefully printed on a thick envelope in the letterbox. Using snail mail, it is possible to trade postcards, stamps and anything else light and flat enough to fit inside an envelope.

Penpal clubs can be found on the Internet, in magazine columns, newspapers, and sometimes through clubs or special interest groups. Some people are looking for romantic interests, while others just want to find friends. Penpals also make and pass around friendship books.

See also: Esperanto Pen Pal Service