The Mercers' Company, or the Worshipful Company of Mercers, is a livery company of the City of London in the Great Twelve City Livery Companies, and ranks first in the order of precedence of the Companies. Mercery was from a French term meaning a type of haberdasher but has previously been for a variety of goods and ultimately derived from the Latin for merchant.

Today, the Company exists primarily as a charitable institution, supporting a variety of causes. The company's motto is Honor Deo (Latin, "Honour to God").

The Mercers' Company is based at Mercers' Hall, 6 Frederick's Place in the City of London. The City block upon which it stands contains the archaeology of a Roman-British temple known today as Gresham Temple.

Its corporate existence began in the form of a fraternity at least by the reign of King Henry II, in the mid 1100s if not before.

From 1210 to 1214, the first two Mayors of London, Henry FitzAlwyn and Robert FitzAlwyn were claimed to be members, and branch of the company was established at this time, the Company of Merchant Adventurers, who established themselves at Antwerp, the centre of the cloth trade.

Serlo le Mercer was a member of the Company and was one of the negotiators of Magna Carta.

Although of even older origin, the Company was incorporated under a Royal Charter in 1394, its earliest extant Charter. The Company's aim was to act as a trade association for general merchants, and especially for exporters of wool^{[citation needed]} and importers of velvet, silk and other luxurious fabrics (mercers).

From the 14th century onwards the Company held its meetings in the Hospital of St. Thomas of Acon on Cheapside.