| 12297 | January 31 | Event | 1946 – Yugoslavia's new constitution, modeling that of the Soviet Union, establishes six constituent republics (Bosnia and Herzegovina, Croatia, Macedonia, Montenegro, Serbia and Slovenia). |
| 12298 | January 31 | Event | 1946 – The Democratic Republic of Vietnam introduces the đồng to replace the French Indochinese piastre at par. |
| 12299 | January 31 | Event | 1949 – These Are My Children, the first television daytime soap opera is broadcast by the NBC station in Chicago. |
| 12300 | January 31 | Event | 1950 – United States President Harry S. Truman announces a program to develop the hydrogen bomb. |
| 12271 | January 31 | Event | 1747 – The first venereal diseases clinic opens at London Lock Hospital. |
| 12272 | January 31 | Event | 1801 – John Marshall is appointed the Chief Justice of the United States. |
| 12273 | January 31 | Event | 1814 – Gervasio Antonio de Posadas becomes Supreme Director of the United Provinces of the Río de la Plata (present-day Argentina). |
| 12274 | January 31 | Event | 1846 – After the Milwaukee Bridge War, Juneautown and Kilbourntown unify as the City of Milwaukee. |
| 12275 | January 31 | Event | 1848 – John C. Frémont is court-martialed for mutiny and disobeying orders. |
| 12276 | January 31 | Event | 1849 – Corn Laws are abolished in the United Kingdom pursuant to legislation in 1846. |
| 12277 | January 31 | Event | 1862 – Alvan Graham Clark discovers the white dwarf star Sirius B, a companion of Sirius, through an 18.5-inch (47 cm) telescope now located at Northwestern University. |
| 12278 | January 31 | Event | 1865 – American Civil War: The United States Congress passes the Thirteenth Amendment to the United States Constitution, abolishing slavery and submits it to the states for ratification. |
| 12279 | January 31 | Event | 1865 – American Civil War: Confederate General Robert E. Lee becomes general-in-chief. |
| 12280 | January 31 | Event | 1867 – Maronite nationalist leader Youssef Bey Karam leaves Lebanon on board a French ship bound for Algeria. |
| 12281 | January 31 | Event | 1897 – Czechoslav Trade Union Association is founded in Prague. |
| 12282 | January 31 | Event | 1891 – History of Portugal: The first attempt at a Portuguese republican revolution breaks out in the northern city of Porto. |
| 12283 | January 31 | Event | 1900 – Datu Muhammad Salleh is assassinated in Kampung Teboh, Tambunan, ending the Mat Salleh Rebellion. |
| 12284 | January 31 | Event | 1915 – World War I: Germany is the first to make large-scale use of poison gas in warfare in the Battle of Bolimów against Russia. |
| 12285 | January 31 | Event | 1917 – World War I: Germany announces that its U-boats will resume unrestricted submarine warfare after a two-year hiatus. |
| 12286 | January 31 | Event | 1918 – A series of accidental collisions on a misty Scottish night leads to the loss of two Royal Navy submarines with over a hundred lives, and damage to another five British warships. |
| 12287 | January 31 | Event | 1919 – The Battle of George Square takes place in Glasgow, Scotland. |
| 12288 | January 31 | Event | 1929 – The Soviet Union exiles Leon Trotsky. |
| 12289 | January 31 | Event | 1930 – 3M begins marketing Scotch Tape. |
| 12290 | January 31 | Event | 1942 – World War II: Allied forces are defeated by the Japanese at the Battle of Malaya and retreat to the island of Singapore. |
| 12291 | January 31 | Event | 1943 – World War II: German Field Marshal Friedrich Paulus surrenders to the Soviets at Stalingrad, followed 2 days later by the remainder of his Sixth Army, ending one of the war's fiercest battles. |
| 12292 | January 31 | Event | 1944 – World War II: American forces land on Kwajalein Atoll and other islands in the Japanese-held Marshall Islands. |
| 12293 | January 31 | Event | 1944 – World War II: During the Anzio campaign the 1st Ranger Battalion (Darby's Rangers) is destroyed behind enemy lines in a heavily outnumbered encounter at Battle of Cisterna, Italy. |
| 12294 | January 31 | Event | 1945 – US Army private Eddie Slovik is executed for desertion, the first such execution of an American soldier since the Civil War. |
| 12295 | January 31 | Event | 1945 – World War II: About 3,000 inmates from the Stutthof concentration camp are forcibly marched into the Baltic Sea at Palmnicken (now Yantarny, Russia) and executed. |
| 12296 | January 31 | Event | 1945 – World War II: The end of fighting in the Battle of Hill 170 during the Burma Campaign, in which the British 3 Commando Brigade repulsed a Japanese counterattack on their positions and precipitated a general retirement from the Arakan Peninsula. |