In this paper, a robust partial feedback linearizing excitation controller is designed for synchronous generators to enhance the transient stability of single machine infinite bus (SMIB) power systems. The seventh-order dynamical model of synchronous generators including dynamic characteristics of IEEE Type-II exciters are taken into consideration to design this robust excitation controller. Uncertainties associated with both parameters and states are taken into account during the controller design while bounding these uncertainties such that matching conditions are satisfied. In addition, measurement noises are incorporated within the system model which are decoupled through the proposed control scheme and the robustness is ensured through against these noises. The partial feedback linearization method is employed to transform the nonlinear dynamical model into a partially linear system which is then used to design the auxiliary excitation control input for the synchronous generator in an SMIB system. The performance of the proposed excitation control scheme is analyzed on an SMIB system following large disturbances including a comparative study with a conventional power system stabilizer (PSS).