An advance-fee fraud is a confidence trick in which the target is persuaded to advance sums of money in the hope of realizing a very much larger gain. Among the variations on this type of scam, are the Nigerian Letter (also called the 419 fraud, Nigerian scam, Nigerian bank scam, or Nigerian money offer),"Money Transfer hoax," F-Secure the Spanish Prisoner, the Black money scam as well as Russian/Ukrainian scam (also extremely widespread, though far less popular than the former). Both the so-called Russian and Nigerian scams stand for wholly dissimilar organised crime traditions, they therefore tend to use altogether different breeds of approaches.

The 419 scam originated in the early 1980s as the oil-based Nigerian economy declined. Several unemployed university students first used this scam as a means of manipulating business visitors interested in shady deals in the Nigerian oil sector before targeting businessmen in the west, and later the wider population. Scammers in the early-to-mid 1990s targeted companies, sending scam messages via letter, fax, or Telex."International Financial Scams – Internet Dating, Inheritance, Work Permits, Overpayment, and Money-Laundering," United States Department of State The spread of email and easy access to email-harvesting software made the cost of sending scam letters through the Internet inexpensive. In the 2000s, the 419 scam has spurred imitations from other locations in Africa, Asia and Eastern Europe, and, more recently, from North America, Western Europe (mainly UK), and Australia.

The number "419" refers to the article of the Nigerian Criminal Code (part of Chapter 38: "Obtaining Property by false pretences; Cheating") dealing with fraud. The American Dialect Society has traced the term "419 fraud" back to 1992.

The advance-fee fraud is similar to a much older scam known as the Spanish Prisoner scam in which the trickster would tell the scam victim that a (fictitious) rich prisoner had promised to share (non-existent) treasure with the victim if the latter would send money to bribe the prison guards.

Insa Nolte, a lecturer of University of Birmingham's African Studies Department, stated that "The availability of e-mail helped to transform a local form of fraud into one of Nigeria's most important export industries."

Embassies and other organizations warn visitors to various countries about 419. Countries in West Africa with warnings cited include Nigeria, Ghana, Benin,"Benin: 2005 Country Commercial Guide," Embassy of the United States Cotonou, Benin Côte d'Ivoire (Ivory Coast),"WEST AFRICAN ADVANCE FEE SCAMS," United States Embassy in Abidjan, Côte d'Ivoire Togo,"Togo," United States Department of State"Advance Fee Fraud," Hampshire Constabulary Senegal and Burkina Faso. Countries outside of West Africa with 419 warnings cited include South Africa"Advance Fee Fraud," British Bankers' Association, Spain, and The Netherlands."Fraud Scheme Information," United States Consulate General of Amsterdam