Ŝ or ŝ (S circumflex) is a consonant in Esperanto orthography, representing the sound [ʃ].
Esperanto orthography uses a diacritic for all four of its postalveolar consonants, as do most Latin-based Slavic alphabets (Polish is the most notable exception). Letters and digraphs that are similar to ŝ (also based on s) and represent the same sound include Czech, Slovak, Slovene, Serbian Latin, and Croatian š, and English sh. The Cyrillic letter ш represents the same sound.
Ŝ is used in ISO 9:1995 (standard of transliteration into Latin characters of Cyrillic characters) for letter Щ.
Ŝ is the twenty-third letter of the Esperanto alphabet. Although it is written as sx in the x-system and sh in the h-system, it is S with a circumflex (ŝ) when written accented. L. L. Zamenhof, the creator of Esperanto, recommended using sh when ŝ is not available.