The Community Exchange System (CES) is an internet-based global trading network which allows participants to buy and sell goods and services without using a national currency. It may be described as a type of local exchange trading system (LETS) network based on free software. While it can be used as an alternative to traditional currencies such as the Australian dollar or euro or South African rand, the Community Exchange System is a complementary currency in the sense that it functions alongside established currencies.

The CES name was coined by an online web service which started in 2003 in Cape Town, South Africa, as the Cape Town Talent Exchange (CTTE). From there it spread to 99 countries, with the biggest take-up in Australia, where CES Australia was founded in 2011. This original CES takes the idea of LETS and similar systems a step further by providing the means for inter-community trading; it is a global network of communities using non-monetary exchange systems.

The CES is international in scope. It does not have printed money or coins but uses computer technology to serve as an "online money and banking system" or alternative exchange system and as a marketplace. It is an advance from an arrangement in which either one good or service is exchanged for another good or service, or commonly called barter, since it uses a digital unit of value (not the same as a digital currency).

While money typically takes the form of a national currency such as dollars or euros, there have long been other types of "currencies" ranging from simple IOU notes––in which one person declares a debt to a second person in a written document––to more sophisticated programs such as frequent-flyer programs in which points are accumulated in a side-system as a result of purchases. Some communities, typically remote ones, have instituted what is sometimes called a community currency, sometimes with paper notes, such as the Totnes pound in the town of Totnes in the United Kingdom; the idea was to promote local commerce and to "keep money circulating within the town's local economy," according to one report.

The advent of internet technology made alternative (aka complementary) currencies more viable, as databases can keep account of credits and facilitate trading.

A system called the Cape Town Talent Exchange (CTTE) was started in February 2003 in Cape Town by Ashoka fellow Tim Jenkin (also known for a daring prison escape during the apartheid era) and former maths and science teacher and chemical engineer Don Northcott.

The abstract unit of currency (unit of account/value) was called the "Talent", but there were no physical bills or coins made. The purpose was to bring the advantages of a trading network to destitute persons who were unable to get credit or loans using traditional national currencies, as well as assist marginalised communities within the city of Cape Town, such as Khayelitsha, to become self-sustaining. The initial design was as a local moneyless not-for-profit exchange which was similar in most respects to a LETS, which record members trading goods and services using a locally created currency called "LETS Credits".

The exchange later evolved into a more complex system which took advantage of internet technology to reduce the costs of administering the system and allowed expansion to other places, including areas outside of the borders of South Africa. The software permitted the exchange in one city to link up with similar exchanges in other cities to form a global network.