Imperial Eagle, originally named Loudoun (also spelled Louden, Loudin, and Lowden), was a 400-ton (bm) British merchant ship, launched in 1774 at Liverpool. By 1780 her master was S. Rains, her owner Robertson, and her trade a transport out of London. In 1786 she underwent refitting at Shadwell Dock, Thames, London. She then sailed on maritime fur trading ventures in the late 1780s. She was under the command of Captain Charles William Barkley until confiscated in India.

Although some sources, such as Miller, state that Loudon was a former East Indiaman, Hardy and Hardy do not list her under any of the alternative spellings of her name, among the vessels that performed voyages for the British East India Company (EIC). The National Archives's guide to East India Company records in the "British Library: Asian and African Studies (previously Oriental and India Office Library)" also has no record of any vessel bearing her name, in any of its alternative spellings.

As Imperial Eagle, she was among the first ships used in the trading system that developed in the 1780s, in which traders collected sea otter pelts on the Pacific Northwest coast of North America, through trade with the indigenous peoples, and then sold them in Guangzhou (Canton) or Macau, China. The Hawaiian Islands, only recently discovered, were a key way station, with many trading vessels spending the winter there. This maritime fur trading system had originated from the voyages of James Cook, which unexpectedly had revealed the value of sea otter pelts in China.

Although Imperial Eagle was British-owned and operated, the ship masqueraded as a vessel of the fictitious Austrian East India Company, and sailed under the flag of Austria. In fact the ship was owned by various British supercargoes, including some in China and several East India Company directors in England. They called their partnership the Austrian East India Company. John Reid and Daniel Beale were two of the supercargoes. Beale, operating out of Canton, acted as the Prussian agent in that port.

The real Austrian East India Company, also called the Ostend Company, which had existed from 1722 to 1731, had nothing to do with Imperial Eagle. In 1775 the Austrian East India Company was briefly revived when Maria Theresa of Austria granted a charter to William Bolts to establish "Imperial Company of Trieste", which operated until 1785, when it went bankrupt. John Reid was the agent of his company in Canton; he was also one of the owners of Imperial Eagle.

The ship's owners changed her name from Loudoun to Imperial Eagle as an attempt to evade paying for trading licenses from the East India Company and the South Sea Company, which together held a monopoly on all British trade in the Far East and Pacific. The East India Company controlled British trade in Asia and the South Sea Company controlled the Pacific trade on the west coast of the Americas. British traders wanting to work within the companies' domains were legally bound to acquire licenses. The cost was exorbitantly expensive. In the late 18th century a number of independent British traders, notably John Meares, sailed under false flags in order to evade paying for the required licenses. It was akin to flying a flag of convenience but due to the company monopolies, it was illegal for British traders to do so.

Imperial Eagle was a "fine vessel" of 400 tons, ship-rigged and mounting twenty guns. It was very large for its intended use. Its real name is usually spelled Loudoun, but Frances Barkley spelled it Louden and Loudin, and James Colnett spelled it Lowden.

There are only a few printed sources that describe the 1787 voyage of Imperial Eagle or Loudoun. The most thorough is the diary kept by Frances Barkley. George Dixon wrote briefly but vaguely about the ship. John Meares wrote about it in his Voyages, but his account is full of inaccuracies and most of the references to Imperial Eagle are deliberately misleading. Meares, who had acquired Barkley journal and logbook, published maps he claimed to have made himself, based on his own voyages, but which he copied from Barkley's charts. Another source is the journal of James Colnett.