1612

January–March

• January 6 - Axel Oxenstierna becomes Lord High Chancellor of Sweden. He persuades the Riksdag of the Estates to grant the Swedish nobility the right and privilege to hold all higher offices of government.
• January 10 – Gustavus Adolphus replies to Metropolitan Isidor, Odoevskij and the estates of Novgorod, stating that he himself wishes to assume responsibility for the government of Novgorod and also of all Russians. A number of land grants signed the same day show that the Swedish king has assumed the title of Tsar.
• January 20
• *Rudolf II, Holy Roman Emperor, dies and several candidates vie to succeed him, with Archduke Matthias eventually being elected.
• *An uprising led by Dmitry Pozharsky begins in Moscow against occupying Polish troops.
• February 11 - Battle of Vittsjö: King Gustavus Adolphus of Sweden and 3,000 of his troops are forced to retreat from Denmark. The 17-year old king almost drowns while attempting to ride his horse across a frozen lake, but is rescued by two other members of his cavalry. The horse is lost.
• March 2 - The False Dmitry III, one of three pretenders to the Russian throne who all claim to be sons of Ivan the Terrible, is recognized as Tsar of Russia by the Cossacks.
• March 12 - At Daulambapur, near Kamalganj in what is now the Sylhet Division in Bangladesh, a battle takes place between 4,500 troops led by General Islam Khan I of India's Mughal Empire, and 12,000 defenders led by the Afghan warlord Khwaja Usman. The Mughals are almost defeated until Usman is struck in the eye by an arrow fired from a crossbow.

April–June

• April 10 - In England, 12 persons who become known as the Pendle witches allegedly hold a coven at the Malkin Tower in Lancashire on Good Friday, after which 10 people die mysteriously. All but two of the accused witches are tried for causing harm by witchcraft on August 18.
• April 11 - In Lichfield, Edward Wightman, a radical Anabaptist, becomes the last person to be burned at the stake in England as punishment for heresy.
• May 10 - Prince Khurram, the 20-year-old son of the Mughal Emperor Jahangir, marries 19-year-old Arjumand Banu Begum at a ceremony in Delhi. In 1628, Khurram becomes the Emperor Shah Jahan with Arjumand Begum as his chief consort Mumtaz Mahal. Arjumand dies in 1631 and Khurram later commissions and builds the Taj Mahal in her memory.
• May 25 - A Sicilian–Spanish galley fleet defeats the Tunisians at La Goulette after a battle.
• June 13 - Archduke Matthias of Austria is formally elected as the new Holy Roman Emperor.
• June 26 - The coronation of Matthias as Holy Roman Emperor takes place at the Frankfurt Cathedral.

July–September

• July 4 - In what is now Myanmar, Min Khamaung becomes the new King of Arakan upon the death of his father, King Min Razagyi.
• July 22 - Four women and one man are hanged following the Northamptonshire witch trials in England.
• July 24 - Marcantonio Memmo is elected as the Doge of the Republic of Venice on the first ballot of the Venetian council, winning 38 of the 41 votes. Memmo succeeds the late Doge Leonardo Donato, who died on July 16.
• August 20 - Ten Pendle witches are hanged, having been found guilty of practising witchcraft in Lancashire in England.
• August 26 - Battle of Kringen: A Scottish mercenary force is destroyed in Norway.
• September 1 - Battle of Moscow (1612): Led by General Jan Karol Chodkiewicz, a relief force from the Polish-Lithuanian Commonwealth, whose troops had been occupying Moscow for two years, make an unsuccessful attempt to break the Russian siege of the Kremlin, where General Mikolaj Strus and his troops are trapped. Both the Russians and the Commonwealth troops suffer at least 1,000 deaths, but the Russians prevail. General Chodkiewicz tries a second attack the next day and fails.
• September 2 - The Lutheran Duchy of Prussia, a fiefdom within Poland, becomes the first Protestant government to follow the Roman Catholic nations in adopting the Gregorian calendar.
• September 5 - England's East India Company gets its first warships and establishes the "'Honourable East India Company's Marine'" to protect its freighters. The force develops over the centuries into the Royal Indian Navy and, after India's independence in 1947, the Indian Navy.
• September 22 - Retreating Polish and Lithuanian troops burn the Russian city of Vologda in reprisal for their defeat at Moscow.

October–December

• October 27 - Forces of the Polish-Lithuanian Commonwealth, which had been occupying Moscow for more than two years, surrender unconditionally to Russian militia forces and are allowed to leave after the Kremlin is liberated by Prince Dmitry Pozharsky and Prince Kuzma Minin.
• November 20 - The Treaty of Nasuh Pasha is signed, between the Ottoman Empire and the Safavid Empire, with the Ottomans ceding back land they had captured from the Safavids after 1555, in return for Safavid payment of 200 loads of silk.
• November 30 - Battle of Swally: Forces of the British East India Company and Portugal engage off the coast of India, resulting in an English victory.
• December 15 - Simon Marius becomes the first person on Earth to observe the Andromeda Galaxy through a telescope.
• December 28 - Galileo Galilei becomes the first astronomer to observe the planet Neptune when in conjunction with Jupiter. He mistakenly catalogues it as a fixed star, because of its extremely slow motion along the ecliptic. Neptune will not be truly recognized as a planet until 1846, about 234 years later, when Johann Gottfried Galle first sights it in the Berlin Observatory.

Date unknown

• The Nagoya Castle is completed in Japan.
• The Okamoto Daihachi incident in Japan.
• Thomas Shelton's English translation of the first half of Don Quixote is published. It is the first translation of the Spanish novel into any language.