Cornelis de Graeff (15 October 1599 – 4 May 1664), often named Polsbroek or de heer van (lord) Polsbroek during his lifetime, was an influential regent and burgomaster (mayor) of Amsterdam, statesman and diplomat of Holland and the Republic of the United Netherlands at the height of the Dutch Golden Age.

[2] He was one of the leading figures who sought to end the Eighty Years' War between the United Netherlands and the Kingdom of Spain, which took place in 1648 with the Peace of Münster.

[10] Cornelis de Graeff was considered a prudent and skilful statesman and diplomat who was concerned about the balance between the religious and political factions and was held in high esteem by the population.

The proponents of the De Graeff family has shown they had an eye for national politics and tried to find some balance between the House of Orange and the Republicans.

He honored the inheritance of his father, Dirck Jansz Graeff, who was on friendly terms with William the Silent of Orange.

His close relatives included also Hollands writer and poet Pieter Corneliszoon Hooft as one of his uncles, the influential Amsterdam burgomasters and statesmen Andries, Cornelis, Jan Bicker who were his cousins, and burgomaster Frans Banning Cocq (captain of Rembrandt's painting The Night Watch), who was his brother-in-law.

[14] Cornelis de Graeff said that the ancient Amsterdammers had no habit of keeping genealogical records of their families, and knew no more of their generation than what they have learned from their fathers and grandfathers.

As in a real dynasty, members of the two families frequently intermarried in the 17th century in order to keep their political and commercial capital together.

[16] Cornelis de Graeff's coat of arms of origin was quartered and showed the following symbols: The personal coat of arms of Cornelis de Graeff since 1638 is quarterd with a heart shield and shows the following symbols: In 1633 Cornelis de Graeff married Geertruid Overlander van Purmerland (1609–1634), daughter of burgomaster Volkert Overlander and sister of Maria Overlander van Purmerland who was married to Frans Banning Cocq, the captain in Rembrandt's Night Watch.

[17] She died only a few months later and he remarried with Catharina Hooft, nineteen years younger and his first wife's cousin (daughter of her aunt .

They desired the full sovereignty of the individual regions in a form in which the Republic of the United Seven Netherlands was not ruled by a single person.

Instead of a sovereign (or stadtholder) the political and military power was lodged with the States General and with the regents of the cities in Holland.

[19] During the two decades the De Graeff family had a leading role in the Amsterdam administration, the city was at the peak of its political power.

In 1626 he undertook together with his younger brother Dirk de Graeff and Willem Nooms, Lord van Aarlanderveen (he was the father of a illegitimate daughter named Margaretha, whom he, together with Dirk's sister Wendela de Graeff had) an extensive Cavaliersreise, which took them to Paris, Orléans, Blois, Nantes, La Rochelle, Poitiers and in 1628 brought it back to the capital.

[12] In 1636 De Graeff's career began as one of the leaders (Bewindhebber), and later as President, of the Dutch East India Company (VOC).

In the same year he was also the silent force behind the decision to get rid of Andries Bicker, who had become overpowering in the Vroedschap, by appointing him to the Council of States of Holland.

[12] Here, De Graeff enjoyed the intimate trust of stadtholder Frederik Hendrik of Orange, who asked him to lead the peace negotiations with Spain at his side.

His son Jacob de Graeff laid the foundation stone together with Gerbrand Pancras, Sybrant Valckenier and Pieter Schaep.

[24] Van den Vondel also dedicated a poem in praise of his mentor and initiator of the building, Cornelis de Graeff, to this event.

In the center of the stained glass windows of the De Graeffs' baptistery are the coats of arms of Cornelis and his wife Catharina Hooft.

The four strong-headed mayors decided to send Coenraad van Beuningen to Copenhagen to incite Denmark into a war against Sweden.

[33] During the summers the family spent a lot of their time at the Palace Soestdijk, and the sons of De Graeff played with the young William - who became later King of England, Scotland and Ireland and stadtholder of the United Provinces of the Netherlands - at the lake and woods at Palace Soestdijk.

The Dutch Gift was a collection of 28 mostly Italian Renaissance paintings and 12 classical sculptures, along with a yacht, the Mary, and furniture, which was presented to King Charles II of England by the States-General of the Netherlands in 1660.

Cornelis's tomb chapel is to be found of in the Oude Kerk, and after his death his younger brother Andries and the cunning Gillis Valckenier took over his role on the council.