The frigate action of 29 May 1794—not to be confused with the much larger fleet action of 29 May 1794 that took place in the same waters at the same time—was a minor naval engagement of the French Revolutionary Wars between a Royal Navy frigate and a French Navy frigate. The action formed a minor part of the Atlantic campaign of May 1794, a campaign which culminated in the battle of the Glorious First of June, and was unusual in that the French ship Castor had only been in French hands for a few days at the time of the engagement. Castor had previously been a British ship, seized on 19 May by a French battle squadron in the Bay of Biscay and converted to French service while still at sea. While the main fleets manoeuvered around one another, Castor was detached in pursuit of a Dutch merchant ship and on 29 May encountered the smaller independently cruising British frigate HMS Carysfort.