William Douglas (died 1791) was a Scottish ship captain and maritime fur trader during the late 18th century. He worked with the British trader and Captain John Meares, commanding the ship Iphigenia Nubiana. He was involved in the Nootka Crisis of 1789, which brought Britain and Spain to the brink of war. A few years later he was captain of the American ship Grace. In 1791 he partnered with Captain John Kendrick in an attempt to open trade with Japan.
Douglas was an officer on Nootka during Meares's first fur trading voyage to the Pacific Northwest coast from 1786-1787. In 1788, in Macau, China, Meares formed a partnership of several merchants and captains, and purchased two new vessels, the snows Felice Adventurer and Iphigenia Nubiana—generally called Felice and Iphigenia. Meares took command of Felice. He made Douglas captain of Iphigenia and second in command of the expedition, noting in his later account that Douglas "was well acquainted with the coast of America".
Felice Adventurer was of 230 tons burthen (bm) and Iphigenia Nubiana of 200 tons (bm). Meares described them as having bottoms sheathed with copper. Felice had a crew of 50, Iphigenia 40. In order to avoid the cost of acquiring licenses from the East India Company and South Sea Company—required for British merchant ships trading across the Pacific Ocean—and to evade the high port costs China demanded of foreign ships other than those of Portugal, Meares and his partners had Felice and Iphigenia sail under the Portuguese flag. The ships were registered in Macau under a Portuguese merchant named João Carvalho. They sailed under the titular Portuguese command of Francisco José Viana, who pretended to be the captain of Iphigenia, while Meares pretended to be the supercargo of Felice. This tactic of sailing under false colors was not uncommon at the time and was used by other British maritime fur traders such as Charles William Barkley.