| Party: | States Faction |
| Birth Date: | 23 August 1671 |
| Birth Place: | Amsterdam |
| Death Place: | Ilpendam |
| Nationality: | Dutch |
| Spouse: | Cornelis was never married. |
| Residence: | castle Ilpenstein at Ilpendam, country estate Bronstee near Heemstede |
| Occupation: | Landlord |
| Profession: | Canon of St. Pieter at Utrecht |
Cornelis de Graeff (23 August 1671, Amsterdam - 16 February 1719, Ilpendam) was a member of the family De Graeff, a prominent regent family from the Dutch Golden Age. He held the title 20th Free Lord of Purmerland and Ilpendam.
His parents were Pieter de Graeff and his cousin Jacoba Bicker, his younger brother was Johan de Graeff, the Free Lord of Zuid-Polsbroek. His uncle was Johan de Witt, Statesman of the True Freedom, husband of Wendela Bicker, sister of Cornelis' mother Jacoba.
Cornelis de Graeff was a Canon of St. Pieter at Utrecht. Most of the time he resided at his castle Ilpenstein. He also owned Bronstee, a country estate near Heemstede. De Graeff was mentally disturbed and remained unmarried. Since his father's death in 1707 he was under the tutelage of Jacobus de Fremeri, and died at his castle Ilpenstein on February 16, 1719. His successor as Free Lord of Purmerland and Ilpendam was his cousin Gerrit de Graeff. Cornelis' burial chapel is in the Oude Kerk in Amsterdam, in the Sint Cornelis choir, the family grave of the De Graeff family.
At Ilpenstein castle De Graeff had a famous art collection, including Rembrandts Jacob Blessing the Sons of Joseph (the sitters were Wendela de Graeff and her two sons) and the Portrait of Andries de Graeff.[1] The two famous paintings, both by Rembrandt, can be seen today at Wilhelmshöhe in Kassel. De Graeff also owned Frans Halsens painting Catharina Hooft with her Nurse.[2] In 1710 a copy of Rembrandt's 'The Night Watch' was assigned to him. Around 1712, De Graeff's curator De Fremery sold the piece to Pieter van der Lip. Rembrandt expert Abraham Bredius suspected that a second copy of 'The Night Watch', painted by Gerrit Lundens, had gone to Cornelis de Graeff; which turned out to be correct. A painting after Lundens was also present at Pieter de Graeff, after the well-known drawing in the album by De Graeffs uncle Frans Banninck Cocq. This album has been owned by the De Graeff family since 1678.[3]
The personal coat of arms of Cornelis de Graeff is quarterd with a heart shield and shows the following symbols: