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1729 (MDCCXXIX) was a common year starting on Saturday (dominical letter B) of the Gregorian calendar and a common year starting on Wednesday (dominical letter E) of the Julian calendar, the 1729th year of the Common Era (CE) and Anno Domini (AD) designations, the 729th year of the 2nd millennium, the 29th year of the 18th century, and the 10th and last year of the 1720s decade. As of the start of 1729, the Gregorian calendar was 11 days ahead of the Julian calendar, which remained in localized use until 1923.
- July 25 – Seven of the original eight Lords Proprietor sell their tracts within the Province of Carolina back to the British crown. The Province is permanently divided and reorganized into the Royal Colonies of North Carolina and South Carolina.
- July 30 – Baltimore, Maryland is founded.
- August 1 – The Comet of 1729, possibly the largest comet, with the highest apparent magnitude, on record, is discovered by Fr. Nicolas Sarrabat, a professor of mathematics at Marseille.
- September 29–October 5 – Battle of Damghan: The Persians under Nader Shah defeat the Afghans and their allies.
- November – Completion of the first (wooden) Putney Bridge as the only fixed crossing of the River Thames between London Bridge and Kingston in England.
- November 9 – The Treaty of Seville is signed between Great Britain, France, Spain and the Dutch Republic.
- November 29 – Natchez revolt: The worst Indian massacre to take place on Mississippi soil occurs when Natchez people kill 138 Frenchmen, 35 French women, and 56 children at Fort Rosalie (near modern-day Natchez, Mississippi).
- January 19 – William Congreve, English playwright (b. 1670)
- January 31 – Jacob Roggeveen, Dutch explorer (b. 1659)
- March 2 – Francesco Bianchini, Italian philosopher and scientist (b. 1662)
- March 21 – John Law, Scottish economist (b. 1671)
- March 21 – Elżbieta Sieniawska politically influential Polish magnate (b. 1669)
- May 17 – Samuel Clarke, English philosopher (b. 1675)
- June 27 – Élisabeth Jacquet de La Guerre, French harpsichordist and composer (b. 1665)
- July 16 – Johann David Heinichen, German composer (b. 1683)
- August 5 – Thomas Newcomen, English inventor (b. 1663)
- September 1 – Richard Steele, Irish writer and politician (b. 1672)
- September 3 – Jean Hardouin, French scholar (b. 1646)
- September 7 – William Burnet, British Governor of New York and New Jersey (b. 1688)
- October 9 – Richard Blackmore, English physician and writer (b. 1654)
- December 1 – Giacomo F. Maraldi, French-Italian astronomer (b. 1665)
- December 13 – Anthony Collins, English philosopher (b. 1676)
- December – Doamna Marica Brâncoveanu, princess consort of Wallachia (b. 1661)