American Express Company or Amex is an American bank holding company and multinational financial services corporation that specializes in payment cards. It is headquartered at 200 Vesey Street, also known as American Express Tower, in the Battery Park City neighborhood of Lower Manhattan.

Amex is the fourth-largest card network globally based on purchase volume, behind China UnionPay, Visa, and Mastercard. 141.2 million Amex cards were in force worldwide as of December 31, 2023, with an average annual spend per card member of US$24,059. That year, Amex handled over $1.7 trillion in purchase volume on its network. Amex is the 16th largest US bank, with a total of US$270 billion in assets or 1.1% of all assets insured by the FDIC. It is ranked 77th on the Fortune 500 and 28th on the list of the most valuable brands by Forbes. In 2023, it was ranked 63rd in the Forbes Global 2000. American Express National Bank is a direct bank owned by Amex.

Founded in 1850 as a freight forwarding company, Amex introduced financial and travel services during the early 1900s. It developed its 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" advertising campaign was introduced in 1975 and renewed in 2005. In the 1980s, Amex acquired and then divested a stake in Shearson. In the 1990s, it stopped reducing interchange fees for merchants who exclusively accepted Amex cards and expanded market share through targeted marketing campaigns. Amex converted to a bank holding company during the 2008 financial crisis. Amex began operating airport lounges in 2013, offering access to certain cardholders.

Amex had a 9% worldwide market share by transaction volume in 2023. While American Express credit cards are accepted at 99% of U.S. merchants that accept credit cards (Costco being a notable exception), they are much less accepted in Europe and Asia. American Express offers various types of cards including travel and dining cards, everyday spending points cards, and cash back cards. Each category has several card options with different benefits and reward structures. High-profile cards like the Green, Gold, and Platinum cards cater to frequent travelers and diners with perks tailored to these activities.

In 1850, American Express was started as a freight forwarding company in Buffalo, New York. It was founded as a joint-stock corporation by the merger of the cash-in-transit companies owned by Henry Wells (Wells & Company), William G. Fargo (Livingston, Fargo & Company), and John Warren Butterfield (Wells, Butterfield & Company, the successor earlier in 1850 of Butterfield, Wasson & Company). Wells and Fargo also started Wells Fargo & Co. in 1852 when Butterfield and other directors objected to the proposal that American Express extend its operations to California.

American Express initially established its headquarters in a building at the intersection of Jay Street and Hudson Street in what was later called the Tribeca section of Manhattan. For years it enjoyed a virtual monopoly on the movement of express shipments (goods, securities, currency, etc.) throughout New York State. In 1874, American Express moved its headquarters to 65 Broadway in what was becoming the Financial District of Manhattan, a location it was to retain through two buildings.

In 1854, the American Express Co. purchased a lot on Vesey Street in New York City as the site for its stables. The company's first New York headquarters was an 1858 marble Italianate palazzo at 55–61 Hudson Street, which had a busy freight depot on the ground story with a spur line from the Hudson River Railroad. A stable was constructed in 1867, five blocks north at 4–8 Hubert Street. The company prospered sufficiently that headquarters were moved in 1874 from the wholesale shipping district to the budding Financial District and into rented offices in two five-story brownstone commercial buildings at 63 and 65 Broadway that were owned by the Harmony family.

In 1880, American Express built a new warehouse behind the Broadway Building at 46 Trinity Place. The designer is unknown, but it has a façade of brick arches that are reminiscent of pre-skyscraper New York. American Express has long been out of this building, but it still bears a terracotta seal with the American Express Eagle. In 1890–91 the company constructed a new ten-story building by Edward H. Kendall on the site of its former headquarters on Hudson Street. By 1903, the company had assets of some $28 million, second only to the National City Bank of New York among financial institutions in the city. To reflect this, the company purchased the Broadway buildings and site.