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 ^ { 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 we measure spectroscopic redshifts for 15 cluster member galaxies , all of which have strong [ O II ] \lambda \lambda 3727 emission . SPT-CL J2040-4451 has an SZ-measured mass of M _ { 500 ,SZ } = 3.2 \pm 0.8 \times 10 ^ { 14 } M _ { \odot } h _ { 70 } ^ { -1 } , corresponding to M _ { 200 ,SZ } = 5.8 \pm 1.4 \times 10 ^ { 14 } M _ { \odot } h _ { 70 } ^ { -1 } . The velocity dispersion measured entirely from blue star forming members is \sigma _ { v } = 1500 \pm 520 km s ^ { -1 } . The prevalence of star forming cluster members ( galaxies with > 1.5 M _ { \odot } yr ^ { -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 \gtrsim 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 \Lambda CDM cosmological model .