Graphene presents a real need for patterning into very narrow nanostructures to open up a band gap and tune its electrical properties by quantum confinement. A self-assembled silicon-based block copolymer (BCP) is used to pattern chemical vapor deposition-grown graphene to fabricate graphene nanoribbon (GNR) arrays. Best BCP lithographic performances are obtained when the BCP is spin-coated and annealed directly on graphene. Self-assembly on large surfaces (1 cm 2) is achieved in a few minutes, and 11 nm width GNRs are finally obtained. Electrical characterization of these structures such as band gap opening is carried out to confirm the electronic behavior of the graphene nanoribbons. Band gap values of the order of 70 meV were measured. The BCP self-assembly process proposed is scalable, less expensive, and well suited for integration with existing semiconductor fabrication techniques. The lithography procedure developed in this investigation could be generalized to fabricate graphene nanomeshes or quantum dots on large surfaces. Also, this study could concern other two-dimensional materials, for the fabrication of innovative nanostructured materials and functional devices.