The Treaty of Westminster of 1674 was the peace treaty that ended the Third Anglo-Dutch War. Signed by the Dutch Republic and the Kingdom of England, the treaty provided for the return of the colony of New Netherland (now New York) to England and renewed the Treaty of Breda of 1667. The treaty also provided for a mixed commission for the regulation of commerce, particularly in the East Indies.

It was signed on 19 February 1674 Old Style (9 February 1674 New Style) by Charles II of England and ratified by the States General of the Netherlands on 5 March 1674. England was forced to sign the treaty since Parliament would not allow more money to be spent on the war and had become aware of the secret Treaty of Dover in which Charles had promised Louis XIV of France to convert to Catholicism at an opportune moment. The English were dismayed by the unexpected fact that Dutch raiders had managed to capture more English ships than vice versa and that New Amsterdam had been retaken by the Dutch in 1673.

The Third Anglo-Dutch War, or Third Dutch War (Dutch: Derde Engelse Zeeoorlog), was a naval conflict between England, in alliance with France, and the Dutch Republic. It lasted from 7 April 1672 to 19 February 1674, and was a subsidiary of the wider 1672 to 1678 Franco-Dutch War.In the 1670 Secret Treaty of Dover, Charles II of England agreed to support an attack by Louis XIV of France on the Dutch Republic. By doing so, Louis hoped to gain control of the Spanish Netherlands, while Charles sought to restore the damage to his prestige caused by the 1667 Raid on the Medway. Under the treaty, Charles also received secret payments which he hoped would make him financially independent of the English Parliament.

The French offensive in May and June 1672 quickly over-ran most of the Republic, with the exception of the core province of Holland, where they were halted by water defences. In early June, the Anglo-French fleet was badly damaged by the Dutch under Michiel de Ruyter at the Battle of Solebay, ensuring they retained control of vital trade routes.

In late June, Johan de Witt resigned as Grand Pensionary, and Charles' nephew William III of Orange was appointed stadtholder. Charles tried to persuade him to make peace, but William refused; he knew the alliance with France was unpopular in England, while fear of French success brought support from Emperor Leopold and Spain. By the end of 1672, the Dutch had regained much of the territory lost in May, and with hopes of a quick victory gone, Parliament was unwilling to provide further funding.

From June to July 1673, the Dutch and Anglo-French fleets fought three separate battles; although largely inconclusive, they ended any prospect of the Republic being conquered. Instead, Louis focused on taking the Spanish Netherlands, an objective as harmful to English interests as it was to Dutch; domestic opposition forced Charles to agree the Second Peace of Westminster in February 1674.