Electron transport in crystalline TiO2 (rutile phase) is investigated by frequency-dependent conductivity measurements using THz time-domain spectroscopy. Transport is limited by electron-phonon coupling, resulting in a strongly temperature-dependent electron-optical phonon scattering rate, with significant anisotropy in the scattering process. The experimental findings can be described by Feynman polaron theory within the intermediate coupling regime and allow for a determination of electron mobility.