January
- January 2 – Lord Byron marries Anna Isabella Milbanke in Seaham, county of Durham, England.
- January 3 – Austria, Britain, and Bourbon-restored France form a secret defensive alliance treaty against Prussia and Russia.
- January 8 – Battle of New Orleans: American forces led by Andrew Jackson defeat British forces led by Sir Edward Pakenham. American forces suffer around 60 casualties and the British lose about 2,000 (the battle lasts for about 30 minutes).
- January 13 – War of 1812: British troops capture Fort Peter in St. Marys, Georgia, the only battle of the war to take place in the state.
- January 15 – War of 1812: Capture of USS President – American frigate USS President (1800), commanded by Commodore Stephen Decatur, is captured by a squadron of four British frigates.
February
- February 3 – The first commercial cheese factory is founded in Switzerland.
- February 4 – The first Dutch student association, the Groninger Studentencorps Vindicat atque Polit, is founded in the Netherlands. The first rector of the senate is B. J. Winter.
- February 6 – New Jersey grants the first American railroad charter to John Stevens.
- February 17 – The Spanish reconquest of Latin America begins.
- February 18 – The War of 1812 between the United States and the United Kingdom (including Canada) officially ends, following ratification of the Treaty of Ghent (1814) in Washington, D.C.
- February 26 – Napoleonic Wars: Napoleon Bonaparte escapes from Elba.
March
- March 1
- Napoleonic Wars: Napoleon returns to France from his banishment on Elba.
- Georgetown University‘s congressional charter is signed into law, by President James Madison.
- March 15 – Joachim Murat, King of Naples, declares war on Austria in an attempt to save his throne, starting the Neapolitan War.
- March 16 – William I becomes King of the Netherlands.
- March 2–18 – Sri Vikrama Rajasinha of Kandy, the last king in Ceylon, is deposed under the terms of the Kandyan Convention, which results in Ceylon becoming a British colony.
- March 20 – Napoleonic Wars: Napoleon enters Paris, after escaping from Elba with a regular army of 140,000 and a volunteer force of around 200,000, beginning his Hundred Days rule.
April
- April 5–12 – Mount Tambora in the Dutch East Indies blows its top explosively during an eruption, killing upwards of 92,000, and propelling thousands of tons of aerosols (Sulfide gas compounds) into the upper atmosphere (stratosphere). The high level gases reflect sunlight, and cause the widespread cooling (known as a volcanic winter) and heavy rains of 1816, snows in June and July in the northern hemisphere, widespread crop failures, and subsequently famine, which is why 1816 is later known as the Year Without a Summer.
- April 21 – The eastern part of the former Garhwal Kingdom is joined with Kumaon division, under the administration of the British Raj.
- April 24 – The Second Serbian Uprising against Ottoman rule takes place in Takovo, Ottoman Serbia. By the end of the year Serbia is acknowledged as a semi-independent state; the ideals of the First Serbian Uprising have thus been temporarily achieved.
May
- May 3 – Battle of Tolentino: Austria defeats the Kingdom of Naples, which quickly ends the Neapolitan War. Joachim Murat, the defeated King of Naples, is forced to flee to Corsica, and is later executed.
- May 30 – The Arniston, an East Indiaman ship repatriating wounded troops to England from Ceylon, is wrecked near Waenhuiskrans, South Africa, with the loss of 372 of the 378 people on board.
June
- June 9 – The Final Act of the Congress of Vienna is signed: A new European political situation is set. The German Confederation and Congress Poland are created, and the neutrality of Switzerland is guaranteed. Also, Luxembourg declared independence from the French Empire.
- June 15 – The Duchess of Richmond’s ball is held in Brussels, “the most famous ball in history”.
- June 16
- Napoleonic Wars – Battle of Ligny: Napoleon defeats a Prussian army under Gebhard Leberecht von Blücher.
- Napoleonic Wars – Battle of Quatre Bras: Marshal Ney engages Arthur Wellesley, 1st Duke of Wellington, resulting in a tactical and strategic draw.
- June 18 – Napoleonic Wars – Battle of Waterloo: Arthur Wellesley, 1st Duke of Wellington, Gebhard Leberecht von Blücher decisively and this time permanently defeat Napoleon.
- June 22 – Napoleonic Wars: Napoleon abdicates again; Napoleon II (1811–1832), age 4, rules for two weeks (22 June to 7 July).
- June 26 – Napoleonic Wars: Wellington’s advancing Allied Army takes Péronne, Somme on its way to Paris.
July
- July 8 – Napoleonic Wars: Louis XVIII returns to Paris, and is ‘restored’ as King of France (he had declared himself king on 8 June 1795, at the death of his nephew, 10-year-old Louis XVII, and had lived in Westphalia, Verona, Russia, and England).
- July 15 – Napoleonic Wars: Napoleon boards HMS Bellerophon off Rochefort, and surrenders to Captain Frederick Lewis Maitland of the Royal Navy.
August
- August 2 – Napoleonic Wars: Representatives of the United Kingdom, Austria, Russia and Prussia sign a convention at Paris, declaring that Napoleon Bonaparte is “their prisoner” and that “His safe keeping is entrusted to the British Government.”
- August 7 – Napoleonic Wars: Napoleon is transferred to HMS Northumberland, to begin his forced and final second exile, on the remote island of Saint Helena in the South Atlantic Ocean.
September
- September 23 – The Great September Gale of 1815 is the first hurricane to strike New England in 180 years.
- September 26 – Austria, Prussia and Russia sign a Holy Alliance, to uphold the European status quo.
October
- October – Robert Adams, American sailor and the first Westerner to visit Timbuktu, is found wandering the streets of London, starving and half-naked, leading to the invitation for him to tell his story as a Barbary captive, which is later published as The Narrative of Robert Adams.
- October 3 – The Chassigny Martian meteorite falls in Chassigny, Haute-Marne, France.
- October 15 – Napoleonic Wars: Napoleon begins his exile on Saint Helena in the Atlantic Ocean.
- October 23 – A 6.8 earthquake shakes northern China causing many houses and caves to collapse, killing at least 13,000 people.
November
- November 3 – Sir Humphry Davy announces his invention, the Davy lamp (a coal mining safety lamp),
- November 5 – The Ionian Islands become a British protectorate, the United States of the Ionian Islands.
- November 20 – The Napoleonic Wars come to an end after 12 years, with the British government restoring the status quo of France, prior to when the French Revolution began in 1789, after 26 years of turmoil.
- November 27 – The Constitution of the Kingdom of Poland is signed, creating Congress Poland, a constitutional monarchy in personal union with the Russian Empire, under terms agreed at the Congress of Vienna.
December
- December 7 – Marshal Ney is executed in Paris, near the Jardin du Luxembourg.
- December 23 – The novel Emma by Jane Austen is first published, anonymously in London, dated 1816.
- December 25 – The Handel and Haydn Society, the oldest continuously performing arts organization in the United States, gives its first performance, in Boston.
Date unknown
- The first full-blooded European native born in New Zealand, Thomas King, is born in the Bay of Islands.
- The second wave of Amish immigration to North America begins.
- In the United Kingdom, use of the pillory is limited to punishment for perjury.
- Wisden Cricketers’ Almanack retrospectively recognises statistics for first-class cricket in England from this year.