A 2D beam/shell element for nonlinear geometrical and material analysis is presented. The element is based on Simo’s one director tridimensional shell theory. The theory is formulated in stress resultants, so through-the-thickness integration is avoided. Elasto-plastic material behavior with both linear isotropic and kinematic hardening is considered. Yield function is described in terms of 2nd Piola-Kirchhoff stress resultants and is equivalent to von Mises. Three benchmarks are studied in order to assess the nonlinear behavior. First an elastic beam with large rotation and large displacements is presented. Then two thin sheet metal forming problems with moderate large strains are considered. The results obtained are very good and show excellent convergence properties.