Cornelis Jacob van de Graaff (30 March 1734 – 21 April 1812) was a Dutch States Army officer and colonial administrator who served as governor of the Cape from 1785 to 1791.

He arrived with his family in Table Bay on 22 January 1785 and officially took over from Joachim van Plettenberg on 14 February and quickly began to make sweeping changes in the defence system at the Cape.

Van de Graaff started a military training institution, aiming to improve the artillery service and protect the Cape.

The defence system of the northern and eastern frontiers and the local government of the Colony were strengthened by the establishment in 1786 of the Graaff-Reinet district, named after Van de Graaff and his wife.

Van de Graaff resigned from the Dutch military service in 1795, at the time of the revolution in the Netherlands, and fled to Prussia, where he later died.