1666

January–March

• January 17 - The Chair of Saint Peter is set above the altar in St. Peter's Basilica in Rome.
• January 27 - Mughal conquest of Chittagong: Mughal forces of Emperor Aurangzeb, in alliance with the Portuguese, under Shaista Khan and his son Buzurg Umed Khan, expel the Maghs from the Bengal port city of Chittagong, renaming the city as Islamabad.
• February 1 - The joint English and Scottish royal court returns to London as the Great Plague of London subsides.
• March 11 - The tower of St. Peter's Church, Riga, collapses, burying eight people in the rubble.
• March - The Tavernier Blue, precursor to the Hope Diamond, is first recorded, when French gem merchant Jean-Baptiste Tavernier purchases it from the Kollur Mine in the Mughal Empire in uncut form.

  April–June

• April 20 - In colonial British North America, "Articles of Peace and Amity" are signed between the governments of the Province of Maryland and 12 Eastern Algonquian tribes — the Piscataways, Anacostancks, Doegs, Mattawomans, Portobackes, Chopticos, Mikikiwomans, Manasquesends, Chingwawateicks, Hangemaicks, Sacayos, and Panyayos.
• April 23 - On Saint Christopher Island more commonly called St Kitts, a Caribbean Sea island divided between colonies of England and France, a battle near Sandy Point Town over control of the territory ends with a victory by the French over a numerically-superior English force two days after English Deputy Governor William Watts of Anguilla had sent an expedition to capture the neighbouring island of Saint Martin. Governor Watts and the French Governor of Saint-Christophe, Charles de Sales, are both killed in the battle.
• May 12 - In India, General Shivaji Bhonsale of the Maratha Empire arrives at the Agra Fort for a meeting with Emperor Aurangzeb of the Mughal Empire, as part of the terms of peace under the 1665 Treaty of Purandar. After taking offence at the disrespect shown to him, he gets angry and attempts to leave; he and his son Sambhaji are immediately placed under arrest and imprisoned at the fort.
• May 13 - French theologian Louis-Isaac Lemaistre de Sacy is imprisoned in the Bastille after his conviction for heresy in connection with the Jansenist movement. Sacy uses his two and one-half years of incarceration, to create the Bible du Port-Royal, a first French language rendition of the Bible, finishing a translation of the Old Testament from the Vulgate, written in Latin, that had been started by his brother Antoine, and then beginning work on the New Testament.
• May 21
• *The Holy Roman Empire, ruled by Leopold I, repurchases the territory of the Duchy of Opole and Racibórz, which it had ceded to Poland in 1645, for the sum of 120,000 guldens and consolidates it with Upper Silesia. The territory will be ceded from Germany to Poland in 1945 at the end of World War II.
• *Iliaș Alexandru becomes the ruler of Moldavia, part of modern-day Romania.
• June 4 - Molière's comedy of manners The Misanthrope is premièred at the Théâtre du Palais-Royal in Paris by the King's Players with himself in the title role.
• June 6 - Moulai al-Rashid is let into Fes by the city's Jews, establishing the power of Morocco's Alawi dynasty, which will continue into the 21st century.
• June 14 - The Four Days' Battle between the Dutch Republic fleet and the English Royal Navy in the North Sea, one of the longest naval engagements in history, ends with a retreat by the English after having started on June 11. A part of the Second Anglo-Dutch War, the battle ends with a Dutch victory, but heavy losses are sustained on both sides: the English lose 1,000 men and 10 ships are sunk, while the Dutch lose four ships and 1,550 men. Damaged, but not destroyed, the English fleet sets about repairs and refitting, and meets the Dutch fleet again on July 25 in the St. James's Day Battle.

  July–September

• July 1 - During the Portuguese Restoration War between Portugal and Spain, the Battle of the Berlengas ends after four days as a fleet of 15 Spanish warships obtains the surrender of Fort of São João Baptista.
• July 6 - On 3 Muharram 1077 AH on the Muslim calendar, Sa'd ibn Zayd, a descendant of Hasan ibn Ali and of Muhammad becomes the new Sharif of Mecca, in modern-day Saudi Arabia. His ascension to the post follows the death of his father, Zayd ibn Muhsin, who had been the Sharif since 1631.
• July 13 - The Battle of Matwy, the bloodiest engagement of Lubomirski's rebellion, takes place in Poland at the village of Matwy. Jerzy Sebastian Lubomirski, who has led the revolt against Poland's King Jan II Kazimierz, defeats a larger number of troops led by John III Sobieski of the Polish-Lithuanian Commonwealth. Poland and Lithuania sustain 4,000 deaths compared to 200 rebel casualties.
• July 31 - The Agreement of Legonice is signed, with Poland restoring the titles of Jerzy Sebastian Lubomirski and Lubomirski's officers, granting amnesty to all the rebels, and King Jan II Kazimierz abandoning further reform plans.
• August 2 - A hurricane sweeps through the Caribbean Sea near Guadeloupe five days after Barbados colonial Governor Francis Willoughby led a force of two Royal Navy frigates, 12 commandeered vessels and over 1,000 men in a battle against French colonies during the Second Anglo-Dutch War. Willoughby and most of his crew die in the sinking of his flagship, HMS Hope
• August 4 - In the St. James's Day Battle of the Second Anglo-Dutch War, the English Royal Navy, under the command of Prince Rupert of the Rhine and George Monck, 1st Duke of Albemarle, defeats the Dutch Republic navy off the North Foreland of England. The victory comes 6 weeks after the British fleet had sustained a heavy loss in the Four Days' Battle. The Dutch ships Sneek and Tholen are sunk, with the loss of 800 men, while 300 Englishmen die in the sinking of HMS Resolution.
• August 17 - In India, General Shivaji Bhonsale, future ruler of the Maratha Empire, and his son Sambhaji escape from house arrest at the Agra Fort, where they have been held prisoner since May 12.
• August 19 - Rear Admiral Robert Holmes leads an English Royal Navy raid on the Dutch island of Terschelling, destroying 150 merchant ships in the Vlie estuary over a period of two days, and pillaging the town of West-Terschelling. The action becomes known as "Holmes's Bonfire".
• September 2 - The Great Fire of London begins as a blaze in a bakery owned by Thomas Farriner on Pudding Lane, near London Bridge. Over a period of four days, the fire destroys more than 13,000 buildings, but only six people are known to have died, while at least 80,000 are left destitute and homeless. The events are recorded by Samuel Pepys in his diary. The resurveying of property is credited with advancing both cartography and the practices of surveying, as well as resulting in the modern definition by John Ogilby of the statute mile, as 1,760 yards.
• September 4 - Mughal Emperor Aurangzeb grants the French East India Company a royal mandate to trade at the port of Surat.
• September 6 - The Cestui Que Vie Act 1666 is passed by the Parliament of England, to provide for the disposal of the property of missing persons.
• September 16 - The Apostasy of Sabbatai Zevi begins in Istanbul.

  October–December

• October 10 - A "day of humiliation and fasting" is held in London churches a month after the Great Fire of London.
• October 11 - The Sieur de Buat, Captain Henri de Fleury de Coulan of the Army of the Dutch Republic, is beheaded in public at The Hague after being convicted of attempting to overthrow Dutch leader Johan de Witt.
• October 17 - In North America, a French Army regiment led by Alexandre de Prouville de Tracy erects crosses in the Mohawk lands of the eastern Iroquois Confederacy territory along the Mohawk River as part of an invasion that started on September 29. During the expedition, Prouville's forces find four abandoned Mohawk villages in the area, located in the modern U.S. state of New York near the village of Schenectady but never confront any Mohawk defenders, and the French never attempt to enforce their claim.
• October 23 - The most intense tornado on record in English history, an F4 storm on the Fujita scale or T8 on the TORRO scale, strikes the county of Lincolnshire with a path of destruction through the villages of Welbourn, Wellingore, Navenby and Boothby Graffoe, with winds of more than.
• October 26 - Abbas II, the Shah of Iran, dies at the age of 34 after a reign of 24 years, without designating a successor. His 18-year old son Sam Mirza is crowned as the new Safavid dynasty emperor six days later.
• October 27 - Robert Hubert, a Frenchman who has made a false confession to having started the Great Fire of London, is executed based on his statements.
• November 28 - The Battle of Rullion Green takes place in the Pentland Hills near Midlothian in Scotland as the culmination of the brief 'Pentland Rising' which began on November 15 as a rebellion by the Covenanters who oppose changes in the Church of Scotland. At least 2,000 men of the Scottish Royal Army, led by General Thomas Dalyell, defeat more than 750 Covenanter rebels who have been under the command of James Wallace of Auchens.
• December 12 - A sobor of the Russian Orthodox Church deposes Patriarch Nikon of Moscow, but accepts his liturgical reforms. Dissenters from these, known as Old Believers, continue into the 21st century.
• December 19 - Lund University is founded in Lund, Sweden.
• December 22 - The French Academy of Sciences, founded by Louis XIV, first meets.