A robust delay compensator has been developed for a class of uncertain nonlinear systems with an unknown constant input delay. The control law consists of feedback terms based on the integral of past control values and a novel filtered tracking er-ror, capable of compensating for input delays. Suitable Lyapun-ov-Krasovskii functionals are used to prove global uniformly ulti-mately bounded (GUUB) tracking, provided certain sufficient gain conditions, dependent on the bound of the delay, are satis-fied. Simulation results illustrate the performance and robustness of the controller for different values of input delay.