We report the results of time-domain thermoreflectance (TDTR) measurements of two strongly bonded metal-oxide systems with unusually large thermal conductances. We find that TDTR data for the epitaxial SrRuO3/SrTiO3 interface is consistent with an interface conductance G>0.8GWm-2K-1. For an Al/MgO interface at a pressure of 60 GPa, we find G≈1.1GWm-2K-1. Both are within 40% of the maximum possible conductance for these systems, as predicted by simple theory.