The recent discovery of single graphene sheets and the remarkable technologies envisioned for graphene-based materials necessitate the ability to assemble and reproduce nano-precise graphene structures. Here we demonstrate an approach to create atomically precise single graphene structures by applying tensile load to single sheets of graphene that feature specific patterns of vacancies. We report a computational nanoengineering approach that utilizes the first principles based reactive force field potential (ReaxFF), applied here to simulate the fracture mechanics of up to 40,000 fully reactive atoms. We find that the direction and dynamical behavior of graphene fracture can be controlled by the presence of atomistic defects in the form of atomic vacancies placed throughout the sheet. We find that these vacancies produce distinct effects on the resulting fracture surface geometries, defined by the specific patterns in which they occur throughout the 2D structure. For instance, we are able to cut graphene sheets along controlled zigzag patterns on the nanoscale using specific arrangements of vacancies. These findings suggest novel possibilities aimed at cutting and producing atomically precise graphene structures, enabling advances in graphene nanotechnology. The study reported here is the first to apply ReaxFF to model fracture of graphene sheets.