June 6 - Charles X succeeds his cousin Christina to the Swedish throne . After her abdication on the same day, Christina, now the former reigning queen of a Protestant nation, secretly converts to Catholicism.
November 23 - French mathematician, scientist, and religious philosopher Blaise Pascal experiences an intense mystical vision that marks him for life.
Undated
Death of An Calbhach mac Aodha O Conchobhair Donn, last inaugurated King of Connacht (inaugurated 1643).
September 7 - twenty-three Jewish refugees from Brazil settle in New Amsterdam, forming the nucleus of what would be the largest urban Jewish community in history, the Jewish community of New York City.
The Treaty of Pereyaslav was concluded in the city of Pereyaslav during the meeting between the Cossacks of the Zaporizhian Host and Tsar Alexey I of Muscovy, following the Khmelnytsky rebellion.