Citrus species grown in Japan are affected by three major viruses: satsuma dwarf virus (SDV), citrus tatter leaf virus (CTLV, apple stem grooving virus), and citrus tristeza virus (CTV). SDV has spread to other countries, such as China, Korea, and Turkey, apparently through unchecked budwoods and nursery trees; it is natural to assume that some of these contaminated plants harbored CTLV and CTV as well. Thus, citrus viruses in Japan are not only a domestic problem, they are also transboundary threats to agricultural production. This article reviews the occurrence and history of SDV, CTLV, and CTV in Japan as well as recent research developments in Japan and other countries.