こ, in hiragana or コ in katakana, is one of the Japanese kana, each of which represents one mora.

The shape of these kana comes from the kanji 己.

This character may be supplemented by a dakuten; it becomes ご in hiragana, ゴ in katakana and go in Hepburn romanization.

Also, the pronunciation is affected, transforming into [ɡo] in initial positions and varying between [ŋo] and [ɣo] in the middle of words.

A handakuten (゜) does not occur with ko in normal Japanese text, but it may be used by linguists to indicate a nasal pronunciation [ŋo].