This chapter describes magnetic surface anisotropy in single crystal surfaces. Magnetic surface anisotropy is the magnetic contribution to surface energy σ, which depends on the orientation of Ms in the surface. Using standard polar coordinates, with a polar angle θ between Ms, and the surface normal and an azimuth φ with respect to the direction of highest symmetry in the plane, σ is given. Out-of-plane and in-plane anisotropies may be given by the anisotropy constants Ks and Ks,p, respectively, or alternatively by anisotropy fields. Ks, and Ks,p can be determined (a) from film anisotropies; plotted vs. (1/film-thickness); film anisotropies can be determined from FMR, BLS or TOM; (b) from FMR lineshape and surface modes in FMR for bulk crystals; (c) from spin-wave resonances in thin films. Magnetic surface anisotropies of clean single crystal surfaces like Ni(100), Fe(100), and Fe(110) are tabulated.