A forex (or foreign exchange) scam is any trading scheme used to defraud traders by convincing them that they can expect to gain a high profit by trading in the foreign exchange market. Currency trading "has become the fraud du jour" as of early 2008, according to Michael Dunn of the U.S. Commodity Futures Trading Commission. But "the market has long been plagued by swindlers preying on the gullible," according to the New York Times. "The average individual foreign-exchange-trading victim loses about $15,000, according to CFTC records" according to The Wall Street Journal. The North American Securities Administrators Association says that "off-exchange forex trading by retail investors is at best extremely risky, and at worst, outright fraud."

"In a typical case, investors may be promised tens of thousands of dollars in profits in just a few weeks or months, with an initial investment of only $5,000. Often, the investor’s money is never actually placed in the market through a legitimate dealer, but simply diverted – stolen – for the personal benefit of the con artists."

In August, 2008 the CFTC set up a special task force to deal with growing foreign exchange fraud.” In January 2010, the CFTC proposed new rules limiting leverage to 10 to 1, based on " a number of improper practices" in the retail foreign exchange market, "among them solicitation fraud, a lack of transparency in the pricing and execution of transactions, unresponsiveness to customer complaints, and the targeting of unsophisticated, elderly, low net worth and other vulnerable individuals."

Forex market is promoted as zero-sum game, whereas one trader gains another must lose. In truth, market spread, brokerage commissions and other transaction costs are subtracted from the results of all traders, making forex a "negative-sum" game.

These scams might include churning of customer accounts for the purpose of generating commissions, selling software that is supposed to guide the customer to large profits, improperly managed "managed accounts", false advertising, Ponzi schemes and outright fraud. It also refers to any retail forex broker who indicates that trading foreign exchange is a low risk, high profit investment.

The U.S. Commodity Futures Trading Commission (CFTC), which loosely regulates the foreign exchange market in the United States, has noted an increase in the amount of unscrupulous activity in the non-bank foreign exchange industry.

An official of the National Futures Association was quoted as saying, "Retail forex trading has increased dramatically over the past few years. Unfortunately, the amount of forex fraud has also increased dramatically." Between 2001 and 2006 the U.S. Commodity Futures Trading Commission has prosecuted more than 80 cases involving the defrauding of more than 23,000 customers who lost $350 million. From 2001 to 2007, about 26,000 people lost $460 million in forex frauds. CNN quoted Godfried De Vidts, President of the Financial Markets Association, a European body, as saying, "Banks have a duty to protect their customers and they should make sure customers understand what they are doing. Now if people go online, on non-bank portals, how is this control being done?"