Abstract: The purpose of the present invention is to obtain, at a lower cost: an optical glass that has a low temperature coefficient regarding the relative refractive index and that can contribute to correcting the effect of temperature change on image-forming characteristics; and a preform and an optical element that use such an optical glass. This optical glass contains, in mass %, 1.0-27.0% of a SiO2 component, a total of 5.0-34.0% of a Ln2O3 component (wherein, Ln represents at least one selected from the group consisting of La, Gd, Y, and Yb), and more than 30.0% but not more than 65.0% of a BaO component, wherein the contained amount of a B2O3 component is at most 25.0%, and the temperature coefficient (40-60° C.) of the relative refractive index (589.29 nm) falls within the range between +3.0×10?6 and ?10.0×10?6 (° C.?1).