In this paper, we propose a novel free chattering robust nonlinear sliding mode control based on the Lyapunov theory for underactuated two-wheels mobile robots. The salient features of the proposed control method are as: (1) it considers the full dynamics of the system, disturbances, and uncertainties; (2) it has not considered the small signal model of the system that leads to the large signal instability; and (3) the proposed underactuated control results in less costs, least chattering, easy implementation, and no stability issues. The proposed nonlinear controller is designed based on Lyapunov and Lassalle theory. Moreover, we have shown that the proposed controller is robust against disturbances and uncertainties.