A local exchange trading system (also local employment and trading system or local energy transfer system; abbreviated LETS) is a locally initiated, democratically organised, not-for-profit community enterprise that provides a community information service and records transactions of members exchanging goods and services by using locally created currency. LETS allow people to negotiate the value of their own hours or services, and to keep wealth in the locality where it is created.

Similar trading systems around the world are also known as Community Exchange Systems, Mutual Credit trading systems, Clearing Circles, Trade Exchanges or Time Banks. These all use 'metric currencies' – currencies that measure, as opposed to the fiat currencies used in conventional value exchange. These are all a type of alternative or complementary currency.

In the 21st century, the internet-based networks haves been used to link individual LETS systems, into national or global networks.