1645

January–March

• January 3 - The Long Parliament adopts the Directory for Public Worship in England, Wales, Ireland and Scotland, replacing the Book of Common Prayer. Holy Days are not to be observed.
• January 10 - Archbishop of Canterbury William Laud is executed for treason on Tower Hill, London.
• January 14 - English Civil War: Thomas Fairfax is appointed Commander-in-Chief of the Parliamentarians.
• January 29 - English Civil War: Armistice talks open at Uxbridge.
• February 2 - Battle of Inverlochy: The Scottish Covenanters are defeated by Montrose.
• February 15 - English Civil War: The New Model Army is officially founded.
• February 28 - English Civil War: The Uxbridge armistice talks fail.
• March 4 - English Civil War: Prince Rupert leaves Oxford for Bristol.
• March 5 - Thirty Years' War - Battle of Jankau: The armies of Sweden decisively defeat the forces of the Holy Roman Empire, in one of the bloodiest battles of the war, in southern Bohemia, some 50 kilometres southeast of Prague.
• March 31 - Fearing the spread of the Black Death, Edinburgh Town Council prohibits all gatherings except weddings and funerals.

  April–June

• April 3 - The House of Lords passes the Self-denying Ordinance, requiring members of the Parliament of England to resign commissions in the armed services.
• April 10 - Because of the plague, the Edinburgh town council orders that the college graduation ceremony should be moved forward, so that students can leave the city.
• April 23 - English Civil War: One hundred and fifty Irish soldiers bound for service with King Charles I of England are captured at sea by Parliamentarians and killed at Pembroke in Wales.
• May 2 - Thirty Years' War - Battle of Herbsthausen : The Bavarian army, led by Franz von Mercy, catches French forces led by Marshal Henri de la Tour d'Auvergne, Vicomte de Turenne unawares, and heavily defeats them.
• May 9 - Battle of Auldearn: Scottish Covenanters are defeated by Montrose.
• June 1 - English Civil War: Prince Rupert's army sacks Leicester.
• June 10 - English Civil War: Oliver Cromwell is confirmed as the Lieutenant-General of the Cavalry.
• June 14 - English Civil War - Battle of Naseby: 12,000 Royalist forces are beaten by 15,000 Parliamentarian soldiers.
• June 28 - English Civil War: The Royalists lose Carlisle.

  July–September

• July 2 - English Civil War: Battle of Alford - Alford, Aberdeenshire.
• July 10 - English Civil War: Battle of Langport - Cromwell wins in Somerset.
• July 21 - Qing dynasty regent Dorgon issues a queue order ordering all Han Chinese men to shave their forehead, and braid the rest of their hair into a queue, identical to those of the Manchus.
• July 23 - Tsar Alexei Mikhailovich of Russia comes to the throne.
• July 30 - English Civil War: Scottish Covenanters under Lord Leven begin the Siege of Hereford, a Royalist stronghold.
• August 23 - The Treaty of Brömsebro is signed between Sweden and Denmark–Norway, ending the Torstenson War and ceding Jemtland, Herjedalen, Gotland and Ösel to Sweden, which also holds the province of Halland for a period of 30 years, as a guarantee.
• September 1 - English Civil War: Scottish Covenanters abandon the Siege of Hereford and retreat northwards
• September 10 - English Civil War: Prince Rupert surrenders Bristol.
• September 13 - Scotland in the Wars of the Three Kingdoms: Battle of Philiphaugh - The Covenanters under Sir David Leslie defeat the Royalists under Montrose near Selkirk in the Scottish Borders, restoring the power of the Committee of Estates. After the battle, prisoners and 300 camp followers are slaughtered by Covenanters in cold blood.
• September 24 - English Civil War: Battle of Rowton Heath - Parliamentarians defeat the Royalist cavalry.

  October–December

• October 8-14 - English Civil War: The Third siege of Basing House by Oliver Cromwell results in its destruction.
• October 8 - Jeanne Mance founds the Hôtel-Dieu de Montréal, the first hospital in North America.
• October 11 - English Civil War: Re-fortification of Bourne Castle in Lincolnshire against a threatened Royalist attack begins.
• November 20 - The Colegio de Santo Tomas is elevated by Pope Innocent X into the University of Santo Tomas, in his brief In Supreminenti. It has the oldest extant University Charter in the Philippines, as well as the whole of Asia.
• December 18 - English Civil War: The Royalist stronghold of Hereford is seized in a swift attack by Parliamentary forces under John Birch.

  Date unknown

• Bamana forces from Ségou invade the Mali heartland, destroying the Mali Empire after its 400 years as a unified state.
• The Stolberg-Wernigerode branch of the family of the counts of Stolberg and Wernigerode is founded in Germany.
• The Solar cycle enters the 70-year Maunder Minimum, during which sunspots will be rare.
• Wallpaper begins to replace tapestries, as a wall decoration.
• The Roxbury Latin School is founded.