An all-optical terahertz absorption technique for nondestructive characterization of nanometer-scale metal oxide thin films grown on silicon substrates is described. Example measurements of laser-deposited $\mathrm{Ti}{\mathrm{O}}_2$ and atomic layer-deposited films of $\mathrm{Hf}{\mathrm{O}}_2$ are presented to demonstrate applicability to pure ${\mathrm{Y}}_2{\mathrm{O}}_3$ , ${\mathrm{Al}}_2{\mathrm{O}}_3$ , and $\mathrm{V}{\mathrm{O}}_x$ and mixed combinatorial films as a function of deposition conditions and thickness. This technique is also found to be sensitive to $\mathrm{Hf}{\mathrm{O}}_2$ phonon modes in films with a nominal thickness of $5\mathrm{nm}$ .