1440 (MCDXL) was a leap year starting on Friday of the Julian calendar, the 1440th year of the Common Era (CE) and Anno Domini (AD) designations, the 440th year of the 2nd millennium, the 40th year of the 15th century, and the 1st year of the 1440s decade. As of the start of 1440, the Gregorian calendar was 9 days ahead of the Julian calendar, which was the dominant calendar of the time.
|Ab urbe condita||2193|
|Balinese saka calendar||1361–1362|
|English Regnal year||18 Hen. 6 – 19 Hen. 6|
|Chinese calendar||己未年 (Earth Goat)|
4136 or 4076
— to —
庚申年 (Metal Monkey)
4137 or 4077
|- Vikram Samvat||1496–1497|
|- Shaka Samvat||1361–1362|
|- Kali Yuga||4540–4541|
|Japanese calendar||Eikyō 12|
|Minguo calendar||472 before ROC|
|Thai solar calendar||1982–1983|
1566 or 1185 or 413
— to —
1567 or 1186 or 414
- February 21 – The Prussian Confederation is formed.
- April 9 – Christopher of Bavaria is elected King of Denmark.
- April – Murad II lays siege to Belgrade. The city is heavily damaged, but the defenders' use of artillery prevents the Turks from capturing the city.
- September 13 – Breton knight Gilles de Rais is taken into custody, upon an accusation brought against him by the Bishop of Nantes.
- September – The term of Regent of Sweden Karl Knutsson Bonde ends, as newly elected king of Denmark Christopher of Bavaria is also elected king of Sweden.
- October 22 – Gilles de Rais confesses, and is sentenced to death.
- Itzcóatl, Aztec ruler of Tenochtitlan, dies and is succeeded by Moctezuma I (Moctezuma Ilhuicamina).
- Lorenzo Valla's De falso credita et ementita Constantini Donatione declamatio demonstrates that the Donation of Constantine is a forgery.
- Eton College is founded by Henry VI of England.
- Sir Richard Molyneux is appointed constable of Liverpool Castle, in England.
- The Ming Dynasty government of China begins a decade-long series of issuing harsh edicts towards those who illegally mine silver, the latter known as 'miner bandits' (kuangzei), a trend begun in 1438. The government wants to cap the amount of silver circulating into the market, as more grain taxes are converted into silver taxes. The government establishes community night watches known as 'watches and tithings' (baojia), who ensure that illegal mining activities are brought to a halt. However, these are desperate measures, as illegal silver mining continues to thrive as a dangerous but lucrative venture.
- Zhu Quan writes the Cha Pu ("Tea manual") in China.
- March 9 – Frances of Rome, Italian Benedictine nun and saint (b. 1384)
- March 20 – Sigismund Kęstutaitis, Grand Duke of Lithuania (b. 1365)
- April 2 – Giovanni Vitelleschi, Italian Roman Catholic bishop and soldier
- April 6 – Henry Wardlaw, Scottish church leader
- September 20 – Frederick I, Elector of Brandenburg (b. 1371)
- September 30 – Reginald Grey, 3rd Baron Grey de Ruthyn, English soldier and politician
- October 12 – Ginevra d'Este (b. 1419)
- October 26 – Gilles de Rais, French soldier (b. 1404)
- November 13 – Joan Beaufort, Countess of Westmoreland
- date unknown –
- "Itzcóatl, "Serpiente de obsidiana" (1427–1440)" [Itzcóatl, "Obsidian Snake" (1427–1440)]. Arqueologia Mexicana (in Spanish). Retrieved June 6, 2019.