Wa (hiragana: わ, katakana: ワ) is one of the Japanese kana, which each represent one mora.
There is also a small ゎ/ヮ, that is used to write the morae /kwa/ and /gwa/ (くゎ, ぐゎ), which are almost obsolete in contemporary standard Japanese but still exist in the Ryukyuan languages.
A few loanword such as シークヮーサー(shiikwaasa from Okinawan language) and ムジカ・アンティクヮ・ケルン (Musica Antiqua Köln, German early music group) contains this letter in Japanese.
Katakana ワ is also sometimes written with dakuten, ヷ, to represent a /va/ sound in foreign words; however, most IMEs lack a convenient way to write this.
The kana は (ha) is read as “wa” when it represents a particle.