Charles Ponzi (/ˈpɒnzi/; Italian: [ˈpontsi]; born Carlo Pietro Giovanni Guglielmo Tebaldo Ponzi; March 3, 1882 – January 18, 1949) was an Italian charlatan and con artist who operated in the United States and Canada. His aliases included Charles Ponci, Carlo, Benny Broncko and Charles P. Bianchi.

Born in Lugo, Italy, he became known in the early 1920s as a swindler in North America for his money-making scheme. He promised clients a 50% profit within 45 days or 100% profit within 90 days, by buying discounted postal reply coupons in other countries and redeeming them at face value in the U.S. as a form of arbitrage. In reality, Ponzi was paying earlier investors using the investments of later investors. While this type of fraudulent investment scheme was not invented by Ponzi, it became so identified with him that it now is referred to as a "Ponzi scheme". His scheme ran for over a year before it collapsed, costing his "investors" $20 million.

Ponzi may have been inspired by the scheme of William W. Miller (also known as "520% Miller"), a Brooklyn bookkeeper who in 1899 used a similar deception to take in $1 million (approximately $31.8 million in 2024).

Charles Ponzi was born in Lugo, Emilia-Romagna, Kingdom of Italy on March 3, 1882. He told The New York Times he had come from a family in Parma. Ponzi's ancestors had been well-to-do, and his mother continued to use the title "donna", but the family had subsequently fallen upon difficult times and had little money. Ponzi took a job as a postal worker early on, but soon was accepted into the University of Rome La Sapienza. His richer friends considered the university a "four-year vacation", and he was inclined to follow them around to bars, cafés, and the opera. This resulted in Ponzi spending all his money, and four years later he was broke and without a degree. During this time, a number of Italian boys were migrating to the U.S. and returning to Italy as wealthy individuals. Ponzi's family encouraged him to do the same, with the intention of returning his family to its former socio-economic status.

On November 15, 1903, Ponzi arrived in Boston aboard the S.S. Vancouver. By his own account, Ponzi had $2.50 in his pocket (equivalent to $87 in 2024), having gambled away the rest of his life savings during the voyage. "I landed in this country with $2.50 in cash and $1 million in hopes, and those hopes never left me," he later told a reporter for The New York Times. He quickly learned English and spent the next few years doing odd jobs along the East Coast, eventually taking a job as a dishwasher in a restaurant, where he slept on the floor. Ponzi managed to work his way up to the position of waiter, but was fired for theft and shortchanging customers.

In 1907, after several years of failing to achieve success in the U.S., Ponzi moved to Montreal, Quebec, Canada, and became an assistant teller in the newly opened Banco Zarossi, a bank located on Saint Jacques Street started by Luigi "Louis" Zarossi to service the influx of Italian immigrants arriving in the city. By this time, Ponzi had a winning personality and spoke English and French, as well as Italian, which Zuckoff says helped him get the job at the bank. While working there, Ponzi first saw the scheme of "robbing Peter to pay Paul", which later would be called a Ponzi scheme. Zarossi paid 6 percent interest on bank deposits—double the going rate at the time—and his bank was growing rapidly as a result. Ponzi eventually rose to the position of bank manager. However, he found out that the bank was in serious financial trouble, because of bad real estate loans, and that Zarossi was funding the high interest payments not through profit on investments, but by using money deposited in newly opened accounts. The bank eventually failed, and Zarossi fled to Mexico with a large portion of the money belonging to the bank's customers.

Ponzi stayed in Montreal and, for some time, lived at Zarossi's house, helping the man's abandoned family while planning to return to the U.S. and start over. As Ponzi was penniless, this proved to be very difficult. Eventually, he walked into the offices of a former Zarossi customer, Canadian Warehousing, and finding no one there, wrote himself a check for $423.58 in a checkbook he found, forging the signature of Damien Fournier, a director of the company. Confronted by police who had taken note of his large expenditures just after the forged check was cashed, Ponzi held out his wrist and said, "I'm guilty". He ended up spending three years as Inmate #6660 at St. Vincent-de-Paul Federal Penitentiary, a bleak facility located on the outskirts of Montreal. Rather than inform his mother of his imprisonment, he posted her a letter stating that he had found a job as a "special assistant" to a prison warden.

After his release in 1911, Ponzi decided to return to the U.S., but became involved in a scheme to smuggle Italian illegal immigrants across the border. He was caught and spent two years in Atlanta Prison. Here he became a translator for the warden, who was intercepting letters from mobster Ignazio "the Wolf" Lupo. Ponzi ended up befriending Lupo. Another prisoner, Charles W. Morse, became a true role model to Ponzi. Morse, a wealthy Wall Street businessman and speculator, fooled doctors during medical exams by eating soap shavings to give the appearance of ill-health. Morse was soon released from prison. Ponzi completed his prison term following Morse's release, having an additional month added to his term due to his inability to pay a $50 fine.