The compound previously reported as Ba 2Ti 2B 2O 9 has been reformulated as Ba 3Ti 3B 2O 12, or Ba 3Ti 3O 6(BO 3) 2, a new barium titanium oxoborate. Small single crystals have been recovered from a melt with a composition of BaTiO 3:BaTiB 2O 6 (molar ratio) cooled between 1100°C and 850°C. The crystal structure has been determined by X-ray diffraction: hexagonal system, non-centrosymmetric P 6̄2m space group, a=8.7377(11) Å, c=3.9147(8) Å, Z=1, w R( F2)=0.039 for 504 unique reflections. Ba 3Ti 3O 6(BO 3) 2 is isostructural with K 3Ta 3O 6(BO 3) 2. Preliminary measurements of nonlinear optical properties on microcrystalline samples show that the second harmonic generation efficiency of Ba 3Ti 3O 6(BO 3) 2 is equal to 95% of that of LiNbO 3.