In　this　paper　we　present　a　fully　nonlinear　stick-and-spring　model　for　graphene　subjected　to　in-plane　deformations.　The　constitutive　behaviors　of　sticks　and　springs　are　defined,　respectively,　by　the　modified　Morse　potential　and　a　nonlinear　bond　angle　potential.　The　equilibrium　equations　of　the　representative　cell　are　written　considering　large　displacements　of　the　nodes　(atoms)　and　the　stability　of　the　solutions　is　assessed　using　an　energy　criterion.　The　solutions　for　the　uniaxial　load　cases　along　armchair　and　zigzag　directions　show　that　graphene　is　isotropic　for　small　deformations,　while　it　exhibits　anisotropy　when　subjected　to　large　deformations.　Moreover,　graphene　shows　a　negative　Poisson＇s　ratio　after　a　critical　value　of　deformation.　In　the　case　of　equibiaxial　load,　multiple　solutions　of　the　equilibrium　are　found　and　graphene　can　experience　asymmetric　deformations　despite　the　symmetry　of　the　external　loads.　The　nonlinear　formulation　of　the　equilibrium　is　then　linearized　by　introducing　the　hypothesis　of　small　displacements.　The　expressions　of　Young＇s　modulus　and　Poisson＇s　ratio　are　derived.　(c)　2021　Elsevier　Ltd.　All　rights　reserved.