Died in 1665

Jan 12 Pierre de Fermat given credit for early developments that led to infinitesimal calculus, including his technique of adequality. In particular, he is recognized for his discovery of an original method of finding the greatest and the smallest ordinates of curved lines, which is analogous to that of the differential calculus, then unknown, and his research into number theory. He made notable contributions to analytic geometry, probability, and optics. He is best known for Fermat's Last Theorem, which he described in a note at the margin of a copy of Diophantus' Arithmetica
Jan 31 Johannes Clauberg a German theologian and philosopher. Clauberg was the founding Rector of the first University of Duisburg, where he taught from 1655 to 1665. He is known as a "scholastic cartesian"
Feb 16 Stefan Czarniecki a Polish–Lithuanian Commonwealth general and nobleman. In his career he rose from a petty nobleman to a magnate holding one of the highest offices in the Commonwealth, something that was unprecedented in the Commonwealth history. On 22 July 1664 he received the office of the voivode of Kiev and on 2 January 1665, a few weeks before his death, he was given the office of Field Hetman of the Crown of the Polish Kingdom. He is remembered as an accomplished military commander, and regarded as a Polish national hero. His status in Polish history is acknowledged by a mention of his name in the Polish national anthem
Apr 2 Jan Zamoyski (1627–1665) a Polish nobleman , magnate.
Apr 13 William Louis Prince of Anhalt-Köthen a German prince of the House of Ascania and ruler of the principality of Anhalt-Köthen.
May 24 María de Ágreda a Catholic Franciscan nun and author known for reports of bilocation between Spain and New Mexico and West Texas in the 17th century. In religious life, she was known as Sor María de Jesús de Ágreda. Popular culture since the 17th century has also dubbed her as the Lady in Blue and the Blue Nun. She wrote a series of books about the life of Blessed Virgin Mary
May 31 Pieter Jansz. Saenredam Saenredam was a painter of the Dutch Golden Age, known for his distinctive paintings of whitewashed church interiors
Jun 11 Kenelm Digby an English courtier and diplomat. He was also a highly reputed natural philosopher, and known as a leading Roman Catholic intellectual and Blackloist. For his versatility, Anthony à Wood called him the "magazine of all arts"
Jun 13 Egbert Bartholomeusz Kortenaer an admiral of the United Provinces of the Netherlands. His second name is also given as Bartolomeuszoon or Meeuwiszoon. All of these are variations on the patronym "Son of Bartholomew"
Jun 17 Maria Elisabeth of Holstein-Gottorp by marriage landgravine of Hesse-Darmstadt.
Jun 25 Sigismund Francis Archduke of Austria the ruler of Further Austria including Tyrol from 1662 to 1665.
Aug 14 Charles II Duke of Mantua and Montferrat the son of Charles of Gonzaga-Nevers of Rethel, Nevers, Mantua and Montferrat, and Maria Gonzaga. He followed his grandfather Charles I, Duke of Mantua in 1637 as rulers of these lands, the first 10 years under regency of his mother Duchess Maria. Charles sold the Duchies of Nevers and Rethel in 1659 to Cardinal Jules Mazarin, the factual Regent of France, and they became part of France
Aug 28 Elisabetta Sirani an Italian Baroque painter who died in still-unexplained circumstances at the early age of 27.
Sep 12 Jean Bolland a Jesuit priest and prominent Flemish hagiographer.
Sep 17 Philip IV of Spain King of Spain and Portugal as Philip III. He ascended the thrones in 1621 and reigned in Spain until his death and in Portugal until 1640. Philip is remembered for his patronage of the arts, including such artists as Diego Velázquez, and his rule over Spain during the challenging period of the Thirty Years' War
Sep 25 Archduchess Maria Anna of Austria (1610–1665) Electress of Bavaria as the spouse of Maximilian I, Elector of Bavaria. She also served as Regent of Bavaria during the minority of her son
Oct 11 César Duke of Vendôme the son of Henry IV of France and his mistress Gabrielle d'Estrées, and founder of the House of Bourbon-Vendome. He held the titles of 1st Duke of Vendôme, 2nd Duke of Beaufort and 2nd Duke of Étampes, but is also simply known as César de Vendôme. Through his daughter, Élisabeth de Bourbon, César was a great-great-great-grandfather of Louis XV of France, merging thereafter to the French royal line. César de Bourbon is also an ancestor of Juan Carlos I of Spain, of Albert II, King of the Belgians, of Henri, Grand Duke of Luxembourg, and of Vittorio Emanuele, Prince of Naples, a pretender to the Italian throne
Nov 12 Jerzy Białłozor a Polish nobleman, bishop of Smoleńsk since 1658 and Wilno since 21 November 1661, secretary of the King.
Nov 17 John Earle (bishop) an English bishop.
Nov 19 Nicolas Poussin the leading painter of the classical French Baroque style, although he spent most of his working life in Rome. His work is characterized by clarity, logic, and order, and favors line over color. Until the 20th century he remained a major inspiration for such classically oriented artists as Jacques-Louis David, Jean-Auguste-Dominique Ingres and Paul Cézanne
Dec 2 Catherine de Vivonne marquise de Rambouillet a society hostess and a major figure in the literary history of 17th-century France.
Dec 10 Tarquinio Merula an Italian composer, organist, and violinist of the early Baroque era. Although mainly active in Cremona, stylistically he was a member of the Venetian school. He was one of the most progressive Italian composers of the early 17th century, especially in applying newly developed techniques to sacred music
Dec 29 Paweł Jan Sapieha a Polish-Lithuanian nobleman.