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1643 (MDCXLIII) was a common year starting on Thursday of the Gregorian calendar and a common year starting on Sunday of the Julian calendar, the 1643rd year of the Common Era (CE) and Anno Domini (AD) designations, the 643rd year of the 2nd millennium, the 43rd year of the 17th century, and the 4th year of the 1640s decade. As of the start of 1643, the Gregorian calendar was 10 days ahead of the Julian calendar, which remained in localized use until 1923.
|Ab urbe condita||2396|
|Balinese saka calendar||1564–1565|
|English Regnal year||18 Cha. 1 – 19 Cha. 1|
|Chinese calendar||壬午年 (Water Horse)|
4339 or 4279
— to —
癸未年 (Water Goat)
4340 or 4280
|- Vikram Samvat||1699–1700|
|- Shaka Samvat||1564–1565|
|- Kali Yuga||4743–4744|
|Japanese calendar||Kan'ei 20|
|Julian calendar||Gregorian minus 10 days|
|Minguo calendar||269 before ROC|
|Thai solar calendar||2185–2186|
1769 or 1388 or 616
— to —
1770 or 1389 or 617
|Wikimedia Commons has media related to 1643.|
- January – Claudio Monteverdi's opera L'incoronazione di Poppea is first performed, at the Teatro Santi Giovanni e Paolo in Venice.
- January 21 – Abel Tasman sighted the existing island of Tonga.
- February 6 – Abel Tasman sighted the existing Fiji Islands.
- March 13 – First English Civil War – First Battle of Middlewich: The Roundheads rout the Cavaliers at Middlewich in Cheshire, England.
- April 1 – Åmål, Sweden is granted its city charter.
- April 28 – Francisco de Lucena, former Portuguese Secretary of State, is beheaded after being charged with treason.
- May 14 – Louis XIV succeeds Louis XIII as King of France at age 4. His rule will last until his death at age 77 in 1715, a total of 72 years, which will be the longest reign of any European monarch in recorded history.
- May 19
- May 20 – Dutch expedition to Valdivia – A Dutch fleet is spotted outside Carelmapu in Chile, soon after the village and fort is plundered.
- June 30 – First English Civil War – Battle of Adwalton Moor: Cavaliers (supporters of Charles I) gain control of Yorkshire.
- July 1 – The Westminster Assembly of Divines meets for the first time.
- July 5 – First English Civil War – Battle of Lansdowne: Royalists and Parliamentarians battle to a draw.
- July 13 – First English Civil War – Battle of Roundway Down: In England, Lord Henry Wilmot, Earl of Rochester, commanding the Royalist forces, wins a crushing victory over Parliamentarian Sir William Waller.
- August 24 – Dutch expedition to Valdivia – A Ducht fleet establishes a new colony in the ruins of Valdivia in southern Chile.
- September 20 – First English Civil War – First Battle of Newbury: Royalists withdraw to end further bloodshed.
- September 21 – Hong Taiji, Qing dynasty Emperor of China, dies.
- October 8 – The Shunzhi Emperor of China is crowned age 5, having been chosen to succeed his father by the Deliberative Council of Princes and Ministers.
- October 28 – Dutch expedition to Valdivia – The Dutch end their occupation of Valdivia, in Chile.
- November 14 – Empress Meishō abdicates, and Emperor Go-Kōmyō accedes to the throne of Japan.
- November 24 – Battle of Tuttlingen: France is defeated by forces of the Holy Roman Empire.
- December 13 – English Civil War: The Battle of Alton takes place in Hampshire.
- December 25 – Christmas Island in the Indian Ocean is first sighted, by Captain William Mynors of the British East India Company, on the Royal Mary.
- December 28 – Dutch expedition to Valdivia – The failed Ducht expedition arrives back to Recife in Dutch Brazil.
- An Calbhach mac Aedh Ó Conchobhair Donn, The Ó Conchubhair Donn, Chief of the Name of the Clan Ó Conchubhair, is popularly inaugurated as the last King of Connacht in Ireland.
- Baden-Baden is pillaged by the French.
- Evangelista Torricelli invents the mercury barometer.
- Paul de Chomedey, Sieur de Maisonneuve, places the first Mount Royal Cross atop Mount Royal, above Montreal.
- Jean Bolland publishes the first two volumes of the Acta Sanctorum (in Antwerp). This is the beginning of the Bollandists' work.
- Miyamoto Musashi begins to dictate The Book of Five Rings (Go Rin No Sho) to his student; he will complete it in 1654, just before his death.
- Roger Williams, co-founder of Rhode Island, publishes A Key into the Language of America.
- January 2 – Eleonora d'Este, Italian princess, later nun (d. 1722)
- January 4 – Sir Isaac Newton, English scientist  (d. 1727)
- January 7 – Sir Samuel Grimston, 3rd Baronet, English politician (d. 1700)
- January 9 – Eleonoro Pacello, Italian Catholic prelate, Bishop of Pula (1689–1695) (d. 1695)
- January 13 – Axel Wachtmeister, Count of Mälsåker, Swedish field marshal (d. 1699)
- January 25 – John Hayes, English politician (d. 1705)
- January 24 – Charles Sackville, 6th Earl of Dorset, English poet and courtier (d. 1706)
- January 30 – Sir Francis Blundell, 3rd Baronet, Irish politician (d. 1707)
- February 6
- February 15 – García Felipe de Legazpi y Velasco Altamirano y Albornoz, Spanish Catholic prelate, Bishop of Tlaxcala (d. 1706)
- February 25
- March 4 – Fran Krsto Frankopan, Croatian baroque poet, nobleman and politician (d. 1671)
- March 6 – Pierre de Langle, French bishop and theologian (d. 1724)
- March 8 – Nabeshima Naoyuki, Japanese daimyō (d. 1725)
- March 17 – Fabrizio Spada, Italian Catholic cardinal (d. 1717)
- March 23 – Mary of Jesus de León y Delgado, Spanish Dominican lay sister and mystic (d. 1731)
- March 25 – Louis Moréri, French priest and encyclopaedist (d. 1680)
- March 28 – Anthony Dopping, Anglican Bishop of Meath (d. 1697)
- March 29 – Louis Phélypeaux, comte de Pontchartrain (d. 1727)
- April 3 – Charles V, Duke of Lorraine (d. 1690)
- April 6 – Nehemiah Jewett, American colonial politician (d. 1720)
- April 30 – Johann Oswald Harms, German Baroque painter (d. 1708)
- May 3 – Georg Franck von Franckenau, German botanist (d. 1704)
- May 7 – Stephanus Van Cortlandt, first native-born mayor of New York City (d. 1700)
- May 8 – George Louis I, Count of Erbach-Erbach (1672–1693) (d. 1693)
- May 9 – Charles Kirkhoven, 1st Earl of Bellomont, Dutch-born Irish peer (d. 1683)
- May 10 – Gabriel Revel, French painter (d. 1712)
- May 29 – Patrick Lyon, 3rd Earl of Strathmore and Kinghorne, Scottish peer and the son of John Lyon (d. 1695)
- July 3 – Johann Ernst von Thun, Tyrolean Catholic bishop (d. 1709)
- July 26 – Burchard de Volder, Dutch mathematician (d. 1709)
- July 28 – Antonio Tarsia, Italian composer (d. 1722)
- July 29 – Henri Jules, Prince of Condé (d. 1709)
- August 3 – Charles de la Rue, French Jesuit, Latin poet (d. 1725)
- August 16 – Mumtaz Shikoh, Mughal Empire emperor (d. 1647)
- August 18 – William Louis, Prince of Anhalt-Harzgerode (1670–1709) (d. 1709)
- August 21 – King Afonso VI of Portugal, King of Portugal and the Algarves (d. 1683)
- August 26 – Cardinal de Bouillon, French Catholic cardinal (d. 1715)
- September 3 – Lorenzo Bellini, Italian physician, anatomist (d. 1704)
- September 5 – Sir William Portman, 6th Baronet, English politician (d. 1690)
- September 6 – François-Joseph de Beaupoil de Sainte-Aulaire, French poet (d. 1742)
- September 14
- September 17 – Francis Howard, 5th Baron Howard of Effingham, English peer (d. 1694)
- September 18 – Gilbert Burnet, Scottish philosopher and historian (d. 1715)
- September 27 – Solomon Stoddard, pastor of the Congregationalist Church in Northampton, Massachusetts (d. 1729)
- September 30 – Samuel Hoadly, American-born English schoolmaster, writer of educational books (d. 1705)
- October 5 – Zinat-un-Nissa, princess of the Mughal Empire (d. 1721)
- October 14 – Bahadur Shah I, Mughal Emperor of India (d. 1712)
- October 25 – Georg Ludwig Agricola, German composer (d. 1676)
- November 1 – John Strype, English historian and biographer (d. 1737)
- November 4 – Asano Nagatomo, Japanese daimyō who ruled the Akō Domain (d. 1675)
- November 16 – Jean Chardin, French jeweller, traveller (d. 1713)
- November 22 – René-Robert Cavelier, Sieur de La Salle, French explorer (d. 1687)
- November 23 – Eberhard von Danckelmann, Prussian politician (d. 1722)
- December 24 – Israel Kolmodin, Swedish hymnwriter and priest (d. 1709)
- December 28 – Salomon van Til, theologian of the Dutch Reformed Church (d. 1713)
- January 14 – John Bois, English scholar (b. 1560)
- January 20 – Henry Danvers, 1st Earl of Danby, English noble (b. 1573)
- February 11 – Countess Palatine Anna Maria of Neuburg, Duchess of Saxe-Altenburg (b. 1575)
- February 15 – Countess Juliane of Nassau-Dillenburg, Landgravine of Hesse-kassel (b. 1587)
- February 25 – Marco da Gagliano, Italian composer (b. 1582)
- March 1
- April 4 – Simon Episcopius, Dutch theologian (b. 1583)
- [[April 12]
- April 13 – Margherita Farnese, Benedictine nun (b. 1567)
- April 20 – Christoph Demantius, German composer (b. 1567)
- April 28
- May 14 – King Louis XIII of France (b. 1601)
- July 12 – François Duquesnoy, Flemish Baroque sculptor in Rome (b. 1597)
- July 25 – Robert Pierrepont, 1st Earl of Kingston-upon-Hull, English statesman (b. 1584)
- August – Anne Hutchinson, English Puritan preacher (b. 1591)
- August 7 – Margaret of Brunswick-Lüneburg, German noble (b. 1573)
- August 22
- September 15 – Richard Boyle, 1st Earl of Cork, Irish politician (b. 1566)
- September 20, at the Battle of Newbury:
- September 21 – Emperor Hong Taiji of China (b. 1592)
- October 2 – Jean Chalette, French painter (b. 1581)
- October 29 – Brilliana, Lady Harley, English noble, letter writer and war heroine (b. 1598)
- November 3
- November 14
- November 15 – Tachibana Muneshige, Japanese samurai and soldier (b. 1567)
- November 17 – Jean-Baptiste Budes, Comte de Guébriant, Marshal of France (b. 1602)
- November 29
- December 8 – John Pym, English statesman (b. 1583)
- December 10 – Herman Wrangel, Swedish soldier and politician
- December 11
- December 30 – Giovanni Baglione, Italian painter and historian of art (b. 1566)
- approx. date – Henry Glapthorne, English dramatist (b. 1610)
- date unknown