SPT-CL J2040-4451-spectroscopically confirmed at z = 1.478-is the highest-redshift galaxy cluster yet discovered via the Sunyaev-Zel'dovich effect. SPT-CL J2040-4451 was a candidate galaxy cluster identified in the first 720 deg super(2) of the South Pole Telescope Sunyaev-Zel'dovich (SPT-SZ) survey, and has been confirmed in follow-up imaging and spectroscopy. From multi-object spectroscopy with Magellan-I/Baade+IMACS wemeasure spectroscopic redshifts for 15 cluster member galaxies, all of which have strong OII lambdalambda3727 emission. SPT-CL J2040-4451 has an SZ-measured mass of M sub(500,SZ) = 3.2 + or - 0.8 x 10 super(14) M sub(middot in circle) h super(-1) sub(70) , corresponding to M sub(200,SZ) = 5.8 + or - 1.4 x 10 super(14) M sub(middot in circle) h super(-1) sub(70). The velocity dispersion measured entirely from blue star-forming members is sigma sub(v) = 1500 + or - 520 km s super(-1). The prevalence of star-forming cluster members (galaxies with >1.5 M yr super(-1)) implies that this massive, high-redshift cluster is experiencing a phase of active star formation, and supports recent results showing a marked increase in star formation occurring in galaxy clusters at z gap 1.4. We also compute the probability of finding a cluster as rare as this in the SPT-SZ survey to be >99%, indicating that its discovery is not in tension with the concordance LambdaCDM cosmological model.