| 3721 | January 9 | Event | 2005 – The Sudan People's Liberation Movement and the Government of Sudan sign the Comprehensive Peace Agreement to end the Second Sudanese Civil War. |
| 3722 | January 9 | Event | 2007 – Apple CEO Steve Jobs unveils the first iPhone. |
| 3723 | January 9 | Event | 2011 – Iran Air Flight 277 crashes near Orumiyeh in the northeast of the country, killing 77 people. |
| 3724 | January 9 | Event | 2013 – A SeaStreak ferry traveling to lower Manhattan, New York City, crashes into the dock, injuring 85 people. |
| 3725 | January 9 | Event | 2014 – An explosion at a Mitsubishi Materials chemical plant in Yokkaichi, Japan, kills at least five people and injures 17 others. |
| 3726 | January 9 | Event | 2015 – The perpetrators of the Charlie Hebdo shooting in Paris two days earlier are both killed after a hostage situation. Elsewhere, a second hostage situation, related to the Charlie Hebdo shooting, occurs at a Jewish market, Hypercacher, in the eastern |
| 3727 | January 9 | Birth | 727 – Emperor Daizong of Tang (d. 779) |
| 3728 | January 9 | Birth | 1475 – Crinitus, Italian scholar and author (d. 1507) |
| 3729 | January 9 | Birth | 1554 – Pope Gregory XV (d. 1623) |
| 3730 | January 9 | Birth | 1571 – Charles Bonaventure de Longueval, Count of Bucquoy, French commander (d. 1621) |
| 3731 | January 9 | Birth | 1624 – Empress Meishō of Japan (d. 1696) |
| 3732 | January 9 | Birth | 1674 – Reinhard Keiser, German composer (d. 1739) |
| 3733 | January 9 | Birth | 1685 – Tiberius Hemsterhuis, Dutch philologist and critic (d. 1766) |
| 3734 | January 9 | Birth | 1728 – Thomas Warton, English poet, historian, and critic (d. 1790) |
| 3735 | January 9 | Birth | 1735 – John Jervis, 1st Earl of St Vincent, English admiral and politician (d. 1823) |
| 3736 | January 9 | Birth | 1745 – Caleb Strong, American lawyer and politician 6th Governor of Massachusetts (d. 1819) |
| 3737 | January 9 | Birth | 1753 – Luísa Todi, Portuguese soprano and actress (d. 1833) |
| 3738 | January 9 | Birth | 1773 – Cassandra Austen, English painter (d. 1845) |
| 3739 | January 9 | Birth | 1778 – Hammamizade İsmail Dede Efendi, Turkish Ney player and composer (d. 1846) |
| 3740 | January 9 | Birth | 1811 – Gilbert Abbott à Beckett, English journalist and author (d. 1856) |
| 3741 | January 9 | Birth | 1818 – Antoine Samuel Adam-Salomon, French sculptor and photographer (d. 1881) |
| 3742 | January 9 | Birth | 1819 – James Francis, English-Australian businessman and politician 9th Premier of Victoria (d. 1884) |
| 3743 | January 9 | Birth | 1822 – Carol Benesch, Czech-Romanian architect, designed the Peleș Castle (d. 1896) |
| 3744 | January 9 | Birth | 1823 – Friedrich von Esmarch, German surgeon and academic (d. 1908) |
| 3745 | January 9 | Birth | 1829 – Thomas William Robertson, English director and playwright (d. 1871) |
| 3746 | January 9 | Birth | 1829 – Adolf Schlagintweit, German botanist and explorer (d. 1857) |
| 3747 | January 9 | Birth | 1832 – Félix-Gabriel Marchand, Canadian journalist and politician 11th Premier of Quebec (d. 1900) |
| 3748 | January 9 | Birth | 1839 – John Knowles Paine, American composer and academic (d. 1906) |
| 3749 | January 9 | Birth | 1848 – Princess Frederica of Hanover (d. 1926) |
| 3750 | January 9 | Birth | 1849 – John Hartley, English tennis player (d. 1935) |