Derick Isaacs op den Graeff, also Dirk, Dirck, Derrick Isaacs op den Graeff, Opdengraef, Opdengraff as well as Op den Gräff was one of the so-called Original 13, the first closed group of German emigrants to North America, an original founder of Germantown, Pennsylvania, as well as a civic leader. As an early abolitionist He was a signer of the first organized religious protest against slavery in colonial America. He, or his brother Abraham op den Graeff, are briefly mentioned in John Greenleaf Whittier's poem "The Pennsylvania Pilgrim" simply as "Op Den Graaf".