- Jan 23 France & Sweden sign anti-German Treaty of Barwald
Event of Interest
Feb 5 Founder of Rhode Island, Roger Williams arrives in Boston from England
Election of Interest
May 18 John Winthrop is elected 1st Governor of the Massachusetts Bay Colony
- May 20 Magdeburg in Germany seized by forces of the Holy Roman Empire under earl Johann Tilly, most inhabitants massacred, one of the bloodiest incidents of the Thirty Years' War
- May 30 The Treaty of Fontainebleau signed between Maximilian I, Elector of Bavaria, and the Kingdom of France, establishing a secret alliance between them during the Thirty Years' War.
- Jun 19 Peace of Cherasco: Charles de Gonzaga-Nevers becomes duke of Mantua
- Jun 20 The sack of Baltimore: the Irish village of Baltimore is attacked by Algerian pirates
- Sep 13 Admiral Tholen conquers 30+ Spanish frigates
- Sep 17 Battle of Breitenfeld: King Gustaaf Adolf of Sweden defeats Johann Tserclaes, Count of Tilly.
- Oct 10 Saxon army occupies Prague
- Nov 4 Ferdinand of Austria installed as land guardian of South Netherlands
- Nov 7 Pierre Gassendi observes 1st ever transit of Mercury predicted by Kepler
- Dec 6 1st predicted transit of Venus (Kepler) is observed
- Dec 16 Mount Vesuvius in Italy erupts, burying many villages under lava flows and killing around 3,000 people