American Revolutionary War: The Royal Navy defeats the Penobscot Expedition with the most significant loss of United States naval forces prior to the attack on Pearl Harbor.

The American Revolutionary War, also known as the Revolutionary War or American War of Independence, was the armed conflict that comprised the final eight years of the broader American Revolution, in which American Patriot forces organized as the Continental Army and commanded by George Washington defeated the British Army. The conflict was fought in North America, the Caribbean, and the Atlantic Ocean. The war's outcome seemed uncertain for most of the war. But Washington and the Continental Army's decisive victory in the Siege of Yorktown in 1781 led King George III and the Kingdom of Great Britain to negotiate an end to the war in the Treaty of Paris two years later, in 1783, in which the British monarchy acknowledged the independence of the Thirteen Colonies, leading to the establishment of the United States as an independent and sovereign nation.

The Royal Navy (RN) is the naval warfare force of the United Kingdom. It is a component of His Majesty's Naval Service, and its officers hold their commissions from the King. Although warships were used by English and Scottish kings from the early medieval period, the first major maritime engagements were fought in the Hundred Years' War against France. The modern Royal Navy traces its origins to the English Navy of the early 16th century; the oldest of the UK's armed services, it is consequently known as the Senior Service.

The Penobscot Expedition was a 44-ship American naval armada during the Revolutionary War assembled by the Provincial Congress of the Province of Massachusetts Bay. The flotilla of 19 warships and 25 support vessels sailed from Boston on July 19, 1779, for the upper Penobscot Bay in the District of Maine carrying an expeditionary force of more than 1,000 American colonial marines and militiamen. Also included was a 100-man artillery detachment under the command of Lt. Colonel Paul Revere.