|Centuries:||17th century – 18th century – 19th century|
|Decades:||1710s 1720s 1730s – 1740s – 1750s 1760s 1770s|
|Years:||1739 1740 1741 – 1742 – 1743 1744 1745|
|1742 by topic:|
|Arts and Sciences|
|Archaeology – Architecture – Art – Literature (Poetry) – Music – Science|
|Canada –Denmark – France – Great Britain – Ireland – Norway – Scotland –Sweden –|
|Lists of leaders|
|Colonial governors – State leaders|
|Birth and death categories|
|Births – Deaths|
|Establishments and disestablishments categories|
|Establishments – Disestablishments|
|Ab urbe condita||2495|
|British Regnal year||15 Geo. 2 – 16 Geo. 2|
|Chinese calendar||辛酉年 (Metal Rooster)
4438 or 4378
— to —
壬戌年 (Water Dog)
4439 or 4379
|- Vikram Samvat||1798–1799|
|- Shaka Samvat||1663–1664|
|- Kali Yuga||4842–4843|
|Japanese calendar||Kanpō 2
|Julian calendar||Gregorian minus 11 days|
|Minguo calendar||170 before ROC
|Thai solar calendar||2284–2285|
|Wikimedia Commons has media related to 1742.|
1742 (MDCCXLII) was a common year starting on Monday (dominical letter G) of the Gregorian calendar and a common year starting on Friday (dominical letter C) of the Julian calendar, the 1742nd year of the Common Era (CE) and Anno Domini (AD) designations, the 742nd year of the 2nd millennium, the 42nd year of the 18th century, and the 3rd year of the 1740s decade. As of the start of 1742, the Gregorian calendar was 11 days ahead of the Julian calendar, which remained in localized use until 1918.
- January – The House of Commons of Great Britain votes on the alleged rigging of the Chippenham by-election. It becomes a motion of no confidence which leads to the resignation of Robert Walpole.
- January 9 – Robert Walpole made Earl of Orford and resigns as First Lord of the Treasury and Chancellor of the Exchequer, effectively ending his period as Prime Minister of Great Britain. On his formally relinquishing office five days later, he will have served 20 years and 314 days as Prime Minister, the longest single term ever, and also longer than the accumulated terms of any other British Prime Minister.
- January 24 – Charles VII Albert becomes Holy Roman Emperor.
- February 12 – John Carteret, 2nd Lord Carteret becomes Secretary of State for the Northern Department in Great Britain.
- February 16 – Spencer Compton, Earl of Wilmington, becomes Prime Minister of Great Britain.
- April 13 – George Frideric Handel's oratorio The Messiah is first performed in Dublin, Ireland.
- May 17 – Frederick the Great's army defeats Austrians in Chotusitz; later Austria cedes Silesia to Prussia.
- May 24 – War of the Austrian Succession: Battle of Sahay
- July 7 – War of Jenkins' Ear: British troops repel those of Spain (under Montiano) in the Battle of Bloody Marsh in the Province of Georgia.
- July 14 – William Pulteney is created 1st Earl of Bath in Great Britain.
- September – Construction starts on the Foundling Hospital in London.
- November 13 – The Royal Danish Academy of Sciences and Letters is founded.
- December 2 – The Pennsylvania Journal first appears in print in the United States.
- Daniel le Pelley succeeds Nicolas le Pelley as Seigneur of Sark.
- The Kingdom of Prussia captures Jihlava.
- Christian Goldbach formulates Goldbach's conjecture.
- Colin Maclaurin publishes his Treatise on Fluxions.
- Anders Celsius proposes the Celsius temperature scale (see 1741).
- James Bradley succeeds Edmond Halley as Astronomer Royal.
- The University of Erlangen is founded.
- The Lopukhina Conspiracy arises at the Russian court.
- Molde, Norway, becomes a city.
- Eisenach, Germany builds its Stadtschloss (city castle).
- In Peru, Juan Santos takes the name Atahualpa II and begins an ill-fated rebellion against the Spanish rule.
- The Afghan tribes unite as a monarchy.
- Henry Fielding publishes Joseph Andrews.
- Charles Jervas's English translation of Don Quixote is published posthumously. Through a printer's error, the translator's name is printed as Charles Jarvis, leading the book to forever be known as the Jarvis translation. It is acclaimed as the most faithful English rendering of the novel made up to that time.
- Spain completes the construction of Fort Matanzas in the Matanzas Inlet, approximately 15 miles (24 km) south of St. Augustine, Florida.
- Rome decrees that Roman ceremonial practice in Latin (not in Chinese) is to be the law for Chinese missions.
- January 8 – Philip Astley, English circus organizer (d. 1814)
- March 9 – Michael Anckarsvärd, Swedish politician
- March 10 – Sampson Salter Blowers, American lawyer and jurist (d. 1842)
- March 23 – Agha Mohammad Khan Ghajar, Iranian king (d. 1797)
- April 28 – Henry Dundas, British statesman (d. 1811)
- May 6 – Jean Senebier, Swiss pastor and botanist (d. 1809)
- June 25 – Johann Schweighäuser, German classical scholar (d. 1830)
- June 26 – Arthur Middleton, American politician (d. 1787)
- June 28 – William Hooper, American statesman (d. 1790)
- July 21 – John Cleves Symmes, American statesman (d. 1814)
- July 27 – Nathanael Greene, American general (d. 1786)
- August 14 – Pope Pius VII, born Barnaba Niccolò Maria Luigi Chiaramonti, Italian Benedictine (d. 1823)
- September 14 – James Wilson, American politician (d. 1798)
- October 6 – Johan Herman Wessel, Norwegian poet (d. 1785)
- November 5 – Richard Cosway, English artist (d. 1821)
- December 9 – Carl Wilhelm Scheele, Swedish chemist (d. 1785)
- December 16 – Gebhard Leberecht von Blücher, Prussian general (d. 1819)
- December 26 (bapt.) – George Chalmers, Scottish antiquarian (d. 1825)
- date unknown – Rafaela Herrera, Nicaraguan heroine (d. 1805)
- date unknown – Francis Nash, American military officer (d. 1777)
- January 1 – Peregrine Bertie, 2nd Duke of Ancaster and Kesteven, English statesman (b. 1686)
- January 14 – Edmond Halley, English astronomer (b. 1656)
- February 22 – Charles Rivington, English publisher (b. 1688)
- March 23 – Jean-Baptiste Dubos, French author (b. 1670)
- April 2 – James Douglas, Scottish physician and anatomist (b. 1675)
- April 17 – Arvid Horn, Swedish statesman (b. 1664)
- May 13 – Ludwig IX, Landgrave of Hesse-Darmstadt (b. 1719)
- May 21 – Lars Roberg, Swedish physician (b. 1664)
- May 26 – Pylyp Orlyk, Ukrainian Zaporozhian Cossack starshina, diplomat (b. 1672)
- June 18 – John Aislabie, British politician (b. 1670)
- June 27 – Nathan Bailey, English philologist and lexicographer
- July 4 – Guido Grandi, Italian mathematician (b. 1671)
- July 9 – John Oldmixon, English historian (b. 1673)
- July 12 – Evaristo Abaco, Italian composer (b. 1675)
- July 14 – Richard Bentley, English scholar and critic (b. 1662)
- July 19 – William Somervile, English poet (b. 1675)
- August 25 – Carlos Seixas, Portuguese composer (b. 1704)
- September 22 – Frederic Louis Norden, Danish explorer (b. 1708)
- September 27 – Hugh Boulter, Irish Archbishop of Armagh (b. 1672)
- September 28 – Jean Baptiste Massillon, French bishop (b. 1663)
- November 12 – Friedrich Hoffmann, German physician and chemist (b. 1660)
- November 20 – Melchior de Polignac, French diplomat (b. 1661)
- November 24 – Andrew Bradford, American publisher (b. 1686)
- December 31 – Karl III Philip, Elector Palatine (b. 1661)