Zanabazar's square script is a horizontal Mongolian square script (Mongolian: Хэвтээ Дөрвөлжин бичиг, romanized: Hevtee Dörvöljin bichig or Хэвтээ Дөрвөлжин Үсэг, Hevtee Dörvöljin Üseg),[1] an abugida developed by the monk and scholar Zanabazar based on the Tibetan alphabet to write Mongolian.

It read left to right, and employed vowel diacritics above and below the consonant letters.

Only the vowel /a/ is written as an independent letter; other independent vowels, for example those at the start of a word which can't be attached to a consonant, are written by adding the appropriate diacritic to the letter ⟨𑨀‎⟩.

A length mark indicates that the vowel sound is long and a chandrabindu ⟨𑨵‎⟩ indicates that it is nasalised.

The Zanabazar script includes twenty basic consonants used for writing Mongolian, and twenty additional consonants that are used for transcribing Sanskrit, Tibetan, Chinese, and other languages.