A pyramid scheme is a non-sustainable business model that involves the exchange of money primarily for enrolling other people into the scheme, usually without any product or service being delivered. Pyramid schemes have existed for at least a century.

In addition, other methods of conducting business known as multi-level marketing (MLM) and as "matrix schemes" often closely resemble pyramid schemes (although unlike pyramid schemes, which are almost always frauds, MLM and matrix schemes are in many cases regarded — at least legally — as legitimate business methods).

Most pyramid schemes are attempts to confuse potential consumers into complicated but convincingly fool-proof money making scams. The essential idea behind each scam is that the individual only makes one payment, but somehow they are promised to receive exponential benefits from other people as a reward. A common example might be that a victim is enticed with an offer that, for a fee, allows them to sell the same offer to other people. Each sale includes a fee to the original seller. Clearly, the fundamental flaw is that there is no end benefit; the money simply travels up the chain, and only the originator wins in swindling his followers. Furthermore, the people in the worst situation are the ones at the bottom of the pyramid: those who subscribed to the plan, but were not able to recruit any followers themselves. To embellish the act, most such scams will have fake referrals, testimonials, and information.

Although pyramid schemes have been declared illegal in many countries, they still persist in various forms.