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1765 (MDCCLXV) was a common year starting on Tuesday of the Gregorian calendar and a common year starting on Saturday of the Julian calendar, the 1765th year of the Common Era (CE) and Anno Domini (AD) designations, the 765th year of the 2nd millennium, the 65th year of the 18th century, and the 6th year of the 1760s decade. As of the start of 1765, the Gregorian calendar was 11 days ahead of the Julian calendar, which remained in localized use until 1923.
- January 23 – Prince Joseph of Austria marries Princess Maria Josepha of Bavaria in Vienna.
- January 29 – One week before his death, Mir Jafar, who had been enthroned as the Nawab of Bengal and ruler of the Bengali people with the support and protection of the British East India Company, abdicates in favor of his 18-year-old son, Najmuddin Ali Khan. 
- February 8 –
- Frederick the Great, the King of Prussia, issues a decree abolishing the historic punishments against unmarried women in Germany for "sex crimes", particularly the Hurenstrafen (literally "whore shaming") practices of public humiliation. 
- Isaac Barré, a member of the British House of Commons for Wycombe and a veteran of the French and Indian War in the British American colonies, coins the term "Sons of Liberty" in a rebuttal to Charles Townshend's derisive description of the American colonists during the introduction of the proposed Stamp Act. MP Barré notes that "They fled from your tyranny to a then uncultivated and unhospitable country... And yet, actuated by the principles of true English liberty, they met all these hardships with pleasure, compared with those they suffered in their own country, from the hands of those who should have been their friends." American colonists adopt the term for their own organization after reading the accounts of Barré's speech. 
- February 14 – Spain's five-member "special junta", appointed by Prime Minister Jerónimo Grimaldi, delivers its report regarding "ways to address the backwardness of Spain's commerce with its colonies and with foreign nations". The report provides detailed orders to be delivered to José de Gálvez, the visitador general in charge of New Spain. 
- March 9 – After a public campaign by the writer Voltaire, judges in Paris posthumously exonerate Jean Calas of murdering his son. Calas had been tortured and executed in 1762 on the charge, though his son may have committed suicide.
- March 22 – Royal assent is given to the Duties in American Colonies Act 1765, historically referred to as the Stamp Act, imposing the first direct tax levied from Great Britain on the thirteen American colonies, effective November 1.  The revenue measure (which requires the purchase of a stamp to be affixed for validation of all legal documents, but also to licensed newspapers and even playing cards and dice) is made to help defray the costs for British military operations in North America, including the French and Indian War. 
- March 24 – Great Britain passes the Quartering Act, requiring private households in the thirteen American colonies to house British soldiers if necessary.
- April 4 – At Fort Tombecbe, near what is now the town of Epes, Alabama, representatives of the British Empire and of the Choctaw Indian tribe in Mississippi sign a peace treaty in the wake of French cession of claims to the British. A boundary is fixed between land to be occupied by the Choctaws and for lands which British settlers can use; in addition, the British agree to provide a police official and a gunsmith at Fort Tombecbe for the Choctaws to use for trespassing complaints and for weapons repairs. By 1775, however, the Choctaws are outnumbered in Mississippi. 
- April 5 – After completing the portion of the Mason–Dixon line marking the semi-circular boundary between Pennsylvania and Delaware, English surveyors Charles Mason and Jeremiah Dixon begin the two and a half year process of plotting out the 230-mile boundary between Pennsylvania and Maryland along the latitude of 39°43′20″ N. 
- April 14 – Three days after getting the news that the Stamp Act has passed, American colonists invade the British Army arsenal near the New York City Hall and sabotage guns inside by spiking them. 
- April 26 – At Saint Petersburg, German engineer Christian Kratzenstein presents to the Russian Academy of Sciences a perfected version of the arithmetical machine originally invented by Gottfried Leibniz. Kratzenstein claims that his machine solves the problem with the Leibniz machine has with calculations above four digits, perfecting the flaw where the machine is "prone to err whenever it is necessary to make a number of 9999 move to 10000", but the machine is not developed further. 
- May 18 – Not long after British rule has started over the formerly French colony of Quebec, an accidental fire destroys one quarter of the town of Montreal. 
- May 26 – During a stroll in the park "on a fine Sabbath afternoon" at Glasgow Green, Scottish engineer James Watt receives the inspiration that provides the breakthrough in his development of the steam engine; he recounts later that "The idea came into my mind, that as steam was an elastic body it would rush into a vacuum, and if a communication was made between the cylinder and an exhausted vessel, it would rush into it, and might be there condensed without cooling the cylinder... I had not walked further than the Golf-house when the whole thing was arranged in my mind." 
- June 21 – The Isle of Man is brought under British control, the Isle of Man Purchase Act (coming into force 10 May) confirming HM Treasury's purchase of the feudal rights of the Dukes of Atholl, as Lord of Mann over the island, and revesting them into the British Crown.
- July 10 – King George III dismisses George Grenville from the office of Prime Minister of Great Britain, and replaces him with another Whig Party statesman, Charles Watson-Wentworth, Lord Rockingham. 
- July 12 – On orders of Chief Pontiac, War Chief Wahpesah of the Kickapoo people releases British Indian Affairs negotiator George Croghan from 35 days of detention.  At the same time, Pontiac authorizes a Shawnee Chief, Nanicksah, to sign a treaty with the British on behalf of the Great Lakes tribes, settling the French and Indian War. 
- July 13 – Qianlong, the Emperor of China issues a decree that copper engravings be made to depict all of his victories in battle. In the interest of amity with the Chinese, King George III of Great Britain gives priority to the sale of British copper, and King Louis XV of France assents to the use of French artisans. 
- July 21 – Having eliminated all of his rivals for leadership of Persia, Karim Khan Zand returns in triumph to his home in Shiraz and makes it his capital, then begins construction of citadels, mosques, schools and other buildings. 
- July 23 – Headed by Odawa Chief Pontiac and George Croghan, a party of Great Lakes tribesmen and British soldiers travel along the Wabash River and obtain the release of all white prisoners of war remaining in the Miami people and Odawa villages between Ouiatenon (near modern-day Granville, Indiana) and Detroit. 
- July 30 – At Yale College, eight students attack the residence of Yale's President Thomas Clap because of his promotion of "New Light" Calvinist doctrine; and "with Evil Intent" and "with Strong hand burst and take off the gates of the yard of the mansion house and Carry away and with Screaming and Shouting... throw into said House Numbers of large stones with Cattles Horns into the windows of said House."  The students plead guilty and pay nominal fines, and Clap resigns at the end of the 1765-66 school year.
- August 9 – Russian Empress Catherine II issues a decree authorizing the new way to produce vodka (by freezing).
Map of India
in 1765 showing territories loyal to the Marathas
; and the territories of those loyal to the Great Mogul