Using resonance ultrasound spectroscopy, we measured the monocrystal elastic-stiffness coefficients, the Voigt C ij, of TiB2. With hexagonal symmetry, TiB2 exhibits five independent C ij: C 11, C 33, C 44, C 12, C 13. Using Voigt-Reuss-Hill averaging, we converted these monocrystal values to quasiisotropic (polycrystal) elastic stiffnesses. Briefly, we comment on effects of voids. From the C ij, we calculated the Debye characteristic temperature, the Grüneisen parameter, and various sound velocities. Our study resolves the enormous differences between two previous reports of TiB2's C ij.