In this paper the synthesis and conductivities of the garnet-related Li ion conductors, Li5Ln3Sb2O12 (Ln=La, Pr, Nd, Sm, Eu), are reported. These phases show high Li ion conductivity, similar to previously reported for the related Li5La3M2O12 (M=Nb, Ta) materials. Neutron diffraction structural studies are also reported for Li5La3Sb2O12 indicating a cubic unit cell, space group Ia-3d, with Li located in two partially occupied sites.