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1777 (MDCCLXXVII)was a common year starting on Wednesday of the Gregorian calendar and a common year starting on Sunday of the Julian calendar, the 1777th year of the Common Era (CE) and Anno Domini (AD) designations, the 777th year of the 2nd millennium, the 77th year of the 18th century, and the 8th year of the 1770s decade. As of the start of 1777, the Gregorian calendar was 11 days ahead of the Julian calendar, which remained in localized use until 1923.
- January 2 - American Revolutionary War: American forces under the command of George Washington repulsed a British attack at the Battle of the Assunpink Creek near Trenton, New Jersey.
- January 3 – American Revolutionary War – Battle of Princeton: American general George Washington's army defeats British troops.
- January 11 – American Revolutionary War – Battle of the Assunpink Creek: American general George Washington's army repulses a British attack by Lieutenant General Charles Cornwallis, in a second battle at Trenton, New Jersey.
- January 12 – Mission Santa Clara de Asís is founded in what is now Santa Clara, California.
- January 15 – Vermont declares its independence from New York, becoming the Vermont Republic, an independent country, a status it retains until it joins the United States as the 14th state in 1791.
- January 20 – The Continental Congress approves a resolution "that an authentic copy, with names of the signers of the Declaration of independence, be sent to each of the United States. 
- February 24 – King Joseph I of Portugal dies, and is succeeded by his brother and son-in-law Peter III of Portugal, and his daughter Maria I of Portugal.
- March 4 – The Fourth Continental Congress, with John Hancock as President, begins a 199 day session in Philadelphia, lasting until September 18. 
- March 29 and March 30 – Third voyage of James Cook: English explorer Captain Cook discovers Mangaia and Atiu, in the Cook Islands. 
- April 1 – Friedrich Maximilian Klinger's play Sturm und Drang is premiered by the Seyler Theatre Company in Leipzig, giving its name to the whole Sturm und Drang movement in German literature.
- April 13 – American Revolutionary War: Battle of Bound Brook – A British and Hessian force led by Charles Cornwallis surprises a Continental Army outpost in New Jersey, commanded by Major General Benjamin Lincoln.
- April 27 – American Revolutionary War: Battle of Ridgefield – The British Army defeats Patriot militias, galvanizing resistance in the Connecticut Colony.
- May 8 – Richard Brinsley Sheridan's comedy of manners, The School for Scandal, is first performed at the Theatre Royal, Drury Lane in London.
- May 16 – Lachlan McIntosh and Button Gwinnett shoot each other during a duel near Savannah, Georgia. Gwinnett, a signer of the United States Declaration of Independence, dies 3 days later.
- June 13 – American Revolution: The Marquis de Lafayette lands near Georgetown, South Carolina, to help the Continental Congress train its army.
- July 8 – The 1777 Constitution of Vermont is signed, officially abolishing slavery.
- July 6 – American Revolutionary War – Siege of Fort Ticonderoga: After a bombardment by British artillery under General John Burgoyne, American forces retreat from Fort Ticonderoga, New York.
- July 7 – American Revolutionary War – Battle of Hubbardton: British forces capture over 200 of the American rearguard, from Fort Ticonderoga.
- August 6 – American Revolutionary War – Battle of Oriskany: Loyalists gain a tactical victory over Patriots; Iroquois fight on both sides.
- August 16 – American Revolutionary War – Battle of Bennington: British and Brunswicker forces are decisively defeated by American troops.
- August 22 – American Revolutionary War – The Siege of Fort Stanwix is ended by withdrawal of British forces, following a ruse by Benedict Arnold to persuade them that a much larger force is arriving.
- September 3 – American Revolutionary War – Battle of Cooch's Bridge: British and Hessian forces defeat an American militia, in a minor skirmish in New Castle County, Delaware.
- September 11 – American Revolutionary War – Battle of Brandywine: The British gain a major victory in Chester County, Pennsylvania.
- September 19 – American Revolutionary War – First Battle of Saratoga (Battle of Freeman's Farm): Patriot forces withstand a British attack at Saratoga, New York.
- September 26 – American Revolutionary War – British troops occupy Philadelphia; members of the Continental Congress flee to Lancaster, Pennsylvania where they meet an hold a one day session as the Fifth Congress before fleeing again. 
- September 30 – American Revolutionary War – The Sixth Continental Congress opens its session at York, Pennsylvania , and continues for 272 days until June 27, 1778. 
- October 4 – American Revolutionary War – Battle of Germantown: Troops under George Washington are repelled by British troops under Sir William Howe.
- October 6 – American Revolutionary War – Battle of Forts Clinton and Montgomery: British troops capture Fort Clinton and Fort Montgomery (Hudson River), and are able to dismantle the Hudson River Chain.
- October 7 – American Revolutionary War – Second Battle of Saratoga (Battle of Bemis Heights): British General John Burgoyne is defeated by American troops.
- October 17 – American Revolutionary War – Battle of Saratoga: British General John Burgoyne surrenders to the American troops.
- November 15 – American Revolution: After 16 months of debate, the Continental Congress approves the Articles of Confederation, in the temporary American capital at York, Pennsylvania.
- November 17 – American Revolution: The Articles of Confederation are submitted to the states for ratification.
- November 29 – San Jose, California is founded. It is the first pueblo in Spanish Alta California.
- December 18 - The United States celebrates its first Thanksgiving, marking the recent victory by the American rebels over British General John Burgoyne at Saratoga in October.
- December 19 – American Revolutionary War: George Washington's Continental Army goes into winter quarters at Valley Forge, Pennsylvania.
- December 24 – Third voyage of James Cook: English explorer Captain Cook locates Kiritimati (Christmas Island).
- December 30 – Maximilian III Joseph, Elector of Bavaria dies, & is succeeded by his distant cousin Charles Theodore, Elector of Bavaria.
беларуская (тарашкевіца): 1777
srpskohrvatski / српскохрватски: 1777