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

Both represent the sound [se], and when written with dakuten represent the sound [ze].

In the Ainu language, the katakana セ is sometimes written with a handakuten (which can be entered into a computer as either one character (セ゚) or two combined ones (セ゜) to represent the [t͡se] sound, and is interchangeable with ツェ (tse).