I (い in hiragana or イ in katakana) is one of the Japanese kana each of which represents one mora.

In the modern Japanese system of sound order, it occupies the second position of the mora chart, between あ and う. Additionally, it is the first letter in Iroha, before ろ.

Like other vowels, scaled-down versions of the kana (ぃ, ィ) are used to express sounds foreign to the Japanese language, such as フィ (fi).

In some Okinawan writing systems, a small ぃ is also combined with the kana く (ku) and ふ to form the digraphs くぃ kwi and ふぃ hwi respectively, although the Ryukyu University system uses the kana ゐ/ヰ instead.

* When lengthening "-i" or "-e" morae in Japanese braille, a chōon is always used, as is standard in katakana orthography, instead of adding the い / イ kana.