The Japonic languages are a language family believed to descend from a common language known as Proto-Japonic . There is no universally-accepted concrete proof of the relationship between Japonic languages and other languages, but there are a variety of theories each backed up with different scientific evidences. The most credited theory relates the Japonic languages with the extinct language of ancient Goguryeo. Some go further to include both Japonic and Goguryeo in a larger hypothetical language family called the Fuyu languages that would also include scarcely-attested extinct languages associated with ancient Fuyu and Baekje. Another theory relates the Japonic languages to modern Korean based primarily on near-identical grammar, but there is scarce lexical similarity between the two; supporters of the Fuyu languages theory generally do not include modern Korean as part of that family. Yet another theory is the controversial Altaic languages theory, with the even more controversial proposal that Korean, Fuyu languages, Goguryeo, Japonic languages or any combination of the four are also a part of the Altaic language family. As far as lexical studies have shown, the modern living non-Japonic language with the closest lexical similarity to any of the Japonic languages is Uyghur, a Turkic language. In the wake of these theories, some argue that the similarity between all these languages is merely a Sprachbund, and that the attested similarities between some or all of these languages are simply the result of their cultures being close geographic neighbors on the Asian mainland over the course of millennia.

The Japonic languages are:

• Japanese languages (日本語)
  • Eastern Japanese (now represented only partially by the speech of Aogashima, Tokyo , Hachijojima, Tokyo , Minamidaito, Okinawa, Kitadaito, Okinawa, and a few other small islands)
  • Western Japanese (represented by all Mainland Japanese dialects)
    • Eastern Western Japanese dialects , including most dialects east of the Kansai region
    • Western Western Japanese dialects , including most dialects west of the Kanto region

• Ryukyuan languages (琉球語)
  • Amami (奄美語)
    • Northern dialect
      • Tanegashima dialect
      • Yakushima dialect
      • Northern Oshima dialect
    • Southern dialect
      • Southern Oshima dialect
      • Yoron dialect
  • Okinawan (沖縄語)
    • Kunigami dialect (aka Northern Okinawan)
    • Ie dialect
    • Southern dialect (aka Central Okinawan or Standard Okinawan)
      • Mainland dialect
      • Shimajiri dialect (the linguistic affiliations of the Shimajiri dialects are uncertain, but are often included in the Southern dialect because the Shimajiri region is often considered to be part of that region)
  • Miyako (宮古語)
    • Miyako dialect
    • Irabu dialect
  • Yaeyama (八重山語)
    • Ishigaki dialect
    • Iriomote dialect
    • Taketomi dialect
  • Yonaguni (与那国語)