The lifetime of Lambda^0_b is measured using the semileptonic decay Lambda^0_b -> Lambda^+_c l^- nu-bar, where the Lambda^+_c is reconstructed through its decay Lambda^+_c -> pK^- pi^+. The data were collected by the CDF detector at the Tevatron Collider during 1992-1993 and correspond to an integrated luminosity of 110 pb^-1 of ppbar collisions at sqrt s = 1.8 TeV. From a fit to the decay length distribution of the Lambda_c- lepton system from 197 +/- 25 signal events, the lifetime of Lambda^0_b is measured to be 1.32 +/- 0.15 +/- 0.07 ps.