In this work, we provide high-precision thermal characterizations of $\beta \text{-G}{\mathrm{a}}_2{\mathrm{O}}_3$ single crystals across six crystallographic orientations ([001], [010], [100], [012], $\left[\overline{2}01\right]$, and $\left[\overline{1}02\right]$) using time-domain thermoreflectance (TDTR). Our measurements reveal a pronounced anisotropic thermal conductivity. Beyond establishing the benchmark values for bulk conductivity, we report a significant frequency dependence in the measured thermal conductivity that is primarily governed by the $\mathrm{transducer}/\beta \text{-G}{\mathrm{a}}_2{\mathrm{O}}_3$ interface. By varying transducer configurations, we demonstrate that this frequency dependence in TDTR measurements is not an intrinsic bulk characteristic but is instead governed by the boundary conditions at the interface. These findings resolve long-standing discrepancies in reported $\beta \text{-G}{\mathrm{a}}_2{\mathrm{O}}_3$ thermal conductivity data, offering a clearer framework for the thermal design of ultrawide bandgap devices.

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• Acoustic phonons
• Lattice thermal conductivity
• Optical phonons
• Thermal transport