Enhancing the efficiency of thermoelectric devices is critical for their adoption in commercial large-scale applications aimed at converting heat into electricity. To compete with the present mechanical energy generators, thermoelectric materials need to be at least three times more efficient than today's commercial thermoelectrics. This high conversion efficiency corresponds to a thermoelectric figure of merit, zT, of ~ 3, which has remained elusive despite a long history of searching for new thermoelectric materials. The recent discoveries of high zT among Zintl phase compounds such as Yb14MnSb11, EuZn2Sb2, Yb9Mn4.2Sb9, clathrates, and the filled skutterudites show the potential of this class of compounds for more efficient thermoelectric materials. This perspective summarizes the recent progress on Zintl phases studied for thermoelectric applications with a focus on their chemistry, crystal structure, and transport properties.