This Special Issue on Functional Oxide-Based Thin-Film Materials touches on the latest advancements in several aspects related to material science: the synthesis of novel oxide, photoluminescence characteristics, photocatalytic ability, energy storage, light emitter studies, low-emissivity glass coatings, and investigations of both nanostructure and thin-film properties. It represents an amalgamation of specialists working with device applications and shedding light on the properties and behavior of thin-film oxides (e.g., GaOx, Ga2O3, HfO2, LiNbO3, and doped ZnO, among numerous others). The papers cover many aspects of thin-film science and technology, from thin film to nanostructure and from material properties to optoelectronic applications, thus reflecting the many interests of the community of scientists active in the field.