The recent rapid spread of Zika virus and its unexpected linkage to birth defects and an autoimmuneneurological syndrome has generated worldwide concern. Zika virus is a flavivirus like dengue, yellow fever and West Nile viruses. We present the 3.8Å resolution structure of mature Zika virus determined by cryo-electron microscopy. The structure of Zika virus is similar to other known flavivirus structures except for the ~10 amino acids that surround the Asn154 glycosylation site found in each of the 180 envelope glycoproteins that make up the icosahedral shell.