|Centuries:||17th century – 18th century – 19th century|
|Decades:||1690s 1700s 1710s – 1720s – 1730s 1740s 1750s|
|Years:||1718 1719 1720 – 1721 – 1722 1723 1724|
|1721 by topic:|
|Arts and Sciences|
|Archaeology – Architecture – Art – Literature (Poetry) – Music – Science|
|Canada –Denmark – France – Great Britain – Ireland – Norway – Russia – Scotland –Sweden –|
|Lists of leaders|
|Colonial governors – State leaders|
|Birth and death categories|
|Births – Deaths|
|Establishments and disestablishments categories|
|Establishments – Disestablishments|
|Ab urbe condita||2474|
|British Regnal year||7 Geo. 1 – 8 Geo. 1|
|Chinese calendar||庚子年 (Metal Rat)
4417 or 4357
— to —
辛丑年 (Metal Ox)
4418 or 4358
|- Vikram Samvat||1777–1778|
|- Shaka Samvat||1643–1644|
|- Kali Yuga||4822–4823|
|Japanese calendar||Kyōhō 6
|Julian calendar||Gregorian minus 11 days|
|Minguo calendar||191 before ROC
|Thai solar calendar||2263–2264|
|Wikimedia Commons has media related to 1721.|
1721 (MDCCXXI) was a common year starting on Wednesday (dominical letter E) of the Gregorian calendar and a common year starting on Sunday (dominical letter A) of the Julian calendar, the 1721st year of the Common Era (CE) and Anno Domini (AD) designations, the 721st year of the 2nd millennium, the 21st year of the 18th century, and the 2nd year of the 1720s decade. Note that the Julian day for 1721 is 11 calendar days difference, which continued to be used from 1582 until the complete conversion of the Gregorian calendar was entirely done in 1929.
- January 6 – The Committee of Inquiry on the South Sea Bubble in England publishes its findings.
- March 24 – Johann Sebastian Bach's Brandenburg concertos completed and dedicated to Christian Ludwig of Brandenburg-Schwedt.
- April – Pirates John Taylor and Olivier Levasseur capture the 700-ton Portuguese galleon Nossa Senhora do Cabo at Réunion. The total value of treasure on board (from Goa) is estimated as between £100,000 and £875,000, one of the largest pirate hauls ever.
- April 4 – Robert Walpole becomes the first Prime Minister of Great Britain (although this is more a term of disparagement at this time).
- May 8 – Pope Innocent XIII succeeds Pope Clement XI as the 244th pope.
- September 10 – The Treaty of Nystad is signed, ending the Great Northern War.
- November 2 – Peter I is proclaimed the first Emperor of All the Russias. This replaces the 176-year-long Tsardom of Russia with the Russian Empire. It collapses in 1917.
- December 22 – Philip V of Spain signs in Lerma a Royal Decree transforming the Seminary of Saint Rose of Lima in Caracas into the Universidad Real y Pontificia de Caracas.
- José de Azlor y Virto de Vera, Marquis of San Miguel de Aguayo and governor of Spanish Texas, establishes the fort of Presidio La Bahía at its original location on the ruins of the failed French Fort Saint Louis.
- Regular mail service between Long Island and New England is established.
- A suggestion box is developed under the eighth shogun of Japan, Yoshimune Tokugawa.
- January 10 – Johann Philipp Baratier, German scholar (d. 1740)
- February 3 – Friedrich Wilhelm von Seydlitz, Prussian general (d. 1773)
- February 21 – John McKinly, American physician and President of Delaware (d. 1796)
- March 19 – Tobias Smollett, Scottish physician and author (d. 1771)
- April 11 – David Zeisberger, Moravian missionary (d. 1808)
- April 15 – Prince William Augustus, Duke of Cumberland, English military leader (d. 1765)
- April 19 – Roger Sherman, signer of the American Declaration of Independence (d. 1803)
- July 9 – Johann Nikolaus Götz, German poet (d. 1781)
- July 14 – John Douglas, Scottish Anglican bishop and man of letters (d. 1807)
- August 4 – Granville Leveson-Gower, 1st Marquess of Stafford, English politician (d. 1803)
- August 31 – George Hervey, 2nd Earl of Bristol, British statesman (d. 1775)
- September 14 – Eliphalet Dyer, American statesman and judge (d. 1807)
- October 19 – Joseph de Guignes, French orientalist (d. 1800)
- November 9 – Mark Akenside, English poet and physician (d. 1770)
- November 22 – Joseph Frederick Wallet DesBarres, Swiss-born cartographer and Canadian statesman (d. 1824)
- December 6
- December 27 – François Hemsterhuis, Dutch philosopher (d. 1790)
- December 29 – Marquise de Pompadour, mistress of King Louis XV of France (d. 1764)
- February 16 – James Craggs the Younger, English politician (b. 1686)
- February 24 – John Sheffield, 1st Duke of Buckingham and Normanby, English statesman and poet (b. 1648)
- March 16 – James Craggs the Elder, English politician (b. 1657)
- March 19 – Pope Clement XI (b. 1649)
- March 29 – Charles Vane, English pirate
- April 14 – Michel Chamillart, French statesman (b. 1652)
- April – Mary Read, English pirate (b. c. 1695)
- July 8 – Elihu Yale, American benefactor of Yale University (b. 1649)
- July 18 – Antoine Watteau, French painter (b. 1684)
- August 3 – Grinling Gibbons, Dutch-born woodcarver (b. 1648)
- August 13 – Jacques Lelong, French bibliographer (b. 1665)
- September 8
- September 11 – Rudolf Jakob Camerarius, German botanist and physician (b. 1665)
- September 18 – Matthew Prior, British poet and diplomat (b. 1664)
- September 20 – Thomas Doggett, Irish actor (b. c. 1670)
- October 11 – Edward Colston, English merchant and philanthropist (b. 1636)
- December 13 – Alexander Selkirk, Scottish sailor (original "Robinson Crusoe") (b. 1676)
- December 17 – Richard Lumley, 1st Earl of Scarbrough, English statesman (b. 1650)
- date unknown – Sultan Abdullah Khan Abdali, Persian Governor of Herat, Shah of Herat (b. 1670)
- Breverton, Terry (2004). Black Bart Roberts: The Greatest Pirate of Them All. Gretna, LA: Pelican Publishing. p. 57. ISBN 1-58980-233-0.<templatestyles src="Module:Citation/CS1/styles.css"></templatestyles>
- "Sir Robert Walpole". 10. HM Government. Retrieved 2011-11-16.<templatestyles src="Module:Citation/CS1/styles.css"></templatestyles>
- Clear, Todd R.; Cole, George F.; Resig, Michael D. (2006). American Corrections (7th ed.). Thompson. <templatestyles src="Module:Citation/CS1/styles.css"></templatestyles>