An optical glass includes, in terms of mol % of cations, a total amount of La.sup.3+, Y.sup.3+, and Gd.sup.3+ components falling within a range of from 5% to 65% and a total amount of Zr.sup.4+, Hf.sup.4+, and Ta.sup.5+ components failing within a range of from 5% to 65%, and a relationship expressed in Expression (1) given below is satisfied. (La.sup.3++Y.sup.3++Gd.sup.3+)×(Zr.sup.4+ Hf.sup.4++Ta.sup.3+)≥400(%).sup.2.

An optical glass includes, in terms of mol % of cations, a total amount of La.sup.3+, Y.sup.3+, and Gd.sup.3+ components falling within a range of from 5% to 65% and a total amount of Zr.sup.4+, Hf.sup.4+, and Ta.sup.5+ components falling within a range of from 5% to 65%, and a relationship expressed in Expression (1) given below is satisfied. (La.sup.3++Y.sup.3++Gd.sup.3+)×(Zr.sup.4++Hf.sup.4++Ta.sup.5+)≥400 (%).sup.2

An optical glass includes, in terms of mol % of cations, a total amount of La.sup.3+, Y.sup.3+, and Gd.sup.3+ components falling within a range of from 5% to 65% and a total amount of Zr.sup.4+, Hf.sup.4+, and Ta.sup.5+ components failing within a range of from 5% to 65%, and a relationship expressed in Expression (1) given below is satisfied. (La.sup.3++Y.sup.3++Gd.sup.3+)(Zr.sup.4+Hf.sup.4++Ta.sup.3+) 400(%).sup.2

An optical glass with high refractive index and low dispersion, having refractive index nd of 1.78-1.95, Abbe number d of 32-50, and contains no GeO.sub.2, so it is not easily devitrified. An optical glass, represented by cation %, including: 1-20% of Si.sup.4+; 25-60% of B.sup.3+; 10-40% of La.sup.3+; 0-15% of Y.sup.3+; 0-20% of Nb.sup.5+; 0-15% of Ti.sup.4+; 0-10% of Ta.sup.5+; 0-5% of W.sup.6+; 0-15% of Zr.sup.4+; 0-10% of Zn.sup.2+; 0-10% of Bi.sup.3+. An optical glass with excellent transmittance, an optical glass preform and an optical element formed by the above optical glass. The optical element made by the above optical glass and the above glass preform or optical element blank, such as lens, can be used for optical systems.

An optical glass with high refractive index and low dispersion, having refractive index nd of 1.78-1.95, Abbe number vd of 32-50, and contains no GeO.sub.2, so it is not easily devitrified. An optical glass, represented by cation %, including: 1-20% of Si.sup.4+; 25-60% of B.sup.3+; 10-40% of La.sup.3+; 0-15% of Y.sup.3+; 0-20% of Nb.sup.5+; 0-15% of Ti.sup.4+; 0-10% of Ta.sup.5+; 0-5% of W.sup.6+; 0-15% of Zr.sup.4+; 0-10% of Zn.sup.2+; 0-10% of Bi.sup.3+. An optical glass with excellent transmittance, an optical glass preform and an optical element formed by the above optical glass. The optical element made by the above optical glass and the above glass preform or optical element blank, such as lens, can be used for optical systems.

An optical glass includes, in terms of mol % of cations, a total amount of La.sup.3+, Y.sup.3+, and Gd.sup.3+ components falling within a range of from 5% to 65% and a total amount of Zr.sup.4+, Hf.sup.4+, and Ta.sup.5+ components falling within a range of from 5% to 65%, and a relationship expressed in Expression (1) given below is satisfied. (La.sup.3++Y.sup.3++Gd.sup.3+)(Zr.sup.4++Hf.sup.4++Ta.sup.5+)400(%).sup.2.

An optical glass having the following oxides in mass percentage relative to a total mass of the optical glass: 10.0%-30.0% SiO.sub.2, 10.0%-30.0% P.sub.2O.sub.5, 0.1%-5.0% B.sub.2O.sub.3, 0.1%-10.0% Al.sub.2O.sub.3, 0.1%-10.0% Rn oxides, 1.0%-20.0% R oxides, 0.1%-5.0% ZrO.sub.2, 10.0%-30.0% TiO.sub.2, 15.0%-50.0% Nb.sub.2O.sub.5, 0.1%-10.0% Ln oxides, and 0.1%-10.0% WO.sub.3, wherein TiO.sub.2+Nb.sub.2O.sub.5+P.sub.2O.sub.5+the R oxides accounts for 60.01% or above.