The decay Lambda^0_b -> J/psi Lambda is observed in 110 pb^-1 of
ppbar collisions taken at sqrt s = 1.8 TeV.  These data are used to measure a
Lambda^0_b mass of 5621 +/- 4(stat.) +/- 3(sys.) MeV/c^2, and a mass
difference between the Lambda^0_b and the B^0 of 340 +/- 1(sys.) MeV/c^2.  The
production cross section times branching fraction for the decay Lambda^0_b ->
J/psi Lambda relative to that for the decay B^0 -> J/psi K^0_s has been
measured to be 0.27 +/- 0.12(stat.) +/- 0.05(sys.).