American Express Company (Amex) is an American multinational financial services corporation that specializes in payment cards. Headquartered in New York City, it is one of the most valuable companies in the world and one of the 30 components of the Dow Jones Industrial Average. The company's logo, adopted in 1958, is a gladiator or centurion, whose image appears on the company's well-known traveler's cheques, charge cards, and credit cards. It is based in the American Express Tower, located in the Battery Park City neighborhood of Lower Manhattan, where it maintains its corporate offices. The company is the largest provider of traveler's cheques worldwide.

Founded in 1850 as an express mail dispatcher, the company introduced financial and travel services to clientele during the early 1900s. American Express developed their first paper charge card in 1958, gold card in 1966, green card in 1969, platinum card in 1984, and centurion card in 1999. The "Don't Leave Home Without It" ad campaign was introduced in 1975 and renewed in 2005. During the 1980s, the firm invested and divested in the brokerage industry, through a stake in Shearson Lehman Hutton. In the 1990s, they discontinued cutting interchange fees for merchants who exclusively accepted their cards and expanded their market share through targeted marketing campaigns. They converted into a bank holding company during the 2008 financial crisis. The firm launched their airport lounge amenity in 2013.

American Express accounts for 22.9% of the total dollar volume of domestic credit card transactions (as of 2016) with 56.4 million cards in force in the U.S. and 121.7 million cards globally (as of 2021). The average cardholder spends $23,496 annually. In 2017, Forbes named American Express the most valuable brand in global financial services, and 23rd overall, with an estimate brand value of US$24.5 billion. In 2020, Fortune magazine placed the company ninth in their list of Top 100 Companies to Work For feature, based on an employee survey of satisfaction.