The Syriac alphabet (ܐܠܦ ܒܝܬ ܣܘܪܝܝܐ ʾālep̄ bêṯ Sūryāyā) is a writing system primarily used to write the Syriac language since the 1st century. It is one of the Semitic abjads descending from the Aramaic alphabet through the Palmyrene alphabet, and shares similarities with the Phoenician, Hebrew, Arabic and Sogdian, the precursor and a direct ancestor of the traditional Mongolian scripts.

Syriac is written from right to left in horizontal lines. It is a cursive script where most—but not all—letters connect within a word. There is no letter case distinction between upper and lower case letters, though some letters change their form depending on their position within a word. Spaces separate individual words.

All 22 letters are consonants (called ܐܵܬܘܼܬܵܐ‎, ˀātūṯā). There are optional diacritic marks (called ܢܘܼܩܙܵܐ‎, nuqzā) to indicate the vowel (ܙܵܘܥܵܐ‎, zāwˁā) and other features. In addition to the sounds of the language, the letters of the Syriac alphabet can be used to represent numbers in a system similar to Hebrew and Greek numerals.

Apart from Classical Syriac Aramaic, the alphabet has been used to write other dialects and languages. Several Christian Neo-Aramaic languages, from Turoyo to the Northeastern Neo-Aramaic language of Suret, once vernaculars, primarily began to be written in the 19th century. The Serṭā variant has explicitly been adapted to write Western Neo-Aramaic, previously written in the square Maalouli script, developed by George Rizkalla (Rezkallah), based on the Hebrew alphabet. Besides Aramaic, when Arabic began to be the dominant spoken language in the Fertile Crescent after the Islamic conquest, texts were often written in Arabic using the Syriac script as knowledge of the Arabic alphabet was not yet widespread; such writings are usually called Karshuni or Garshuni (ܓܪܫܘܢܝ‎). In addition to Semitic languages, Sogdian was also written with Syriac script, as well as Malayalam, which form was called Suriyani Malayalam.

There are three major variants of the Syriac alphabet: ʾEsṭrangēlā, Maḏnḥāyā and Serṭā.

The oldest and classical form of the alphabet is ʾEsṭrangēlā (ܐܣܛܪܢܓܠܐ‎). The name of the script is thought to derive from the Greek adjective strongýlē (στρογγύλη, 'rounded'), though it has also been suggested to derive from serṭā ʾewwangēlāyā (ܣܪܛܐ ܐܘܢܓܠܝܐ‎, 'gospel character'). Although ʾEsṭrangēlā is no longer used as the main script for writing Syriac, it has received some revival since the 10th century. It is often used in scholarly publications (such as the Leiden University version of the Peshitta), in titles, and in inscriptions. In some older manuscripts and inscriptions, it is possible for any letter to join to the left, and older Aramaic letter forms (especially of ḥeṯ and the lunate mem) are found. Vowel marks are usually not used with ʾEsṭrangēlā, because it is the oldest form of the script and arose before specialized diacritics were developed.

The East Syriac dialect is usually written in the Maḏnḥāyā (ܡܲܕ݂ܢܚܵܝܵܐ‎, 'Eastern') form of the alphabet. Other names for the script include Swāḏāyā (ܣܘܵܕ݂ܵܝܵܐ‎, 'conversational' or 'vernacular', often translated as 'contemporary', reflecting its use in writing modern Neo-Aramaic), ʾĀṯōrāyā (ܐܵܬ݂ܘܿܪܵܝܵܐ‎, 'Assyrian', not to be confused with the traditional name for the Hebrew alphabet), Kaldāyā (ܟܲܠܕܵܝܵܐ‎, 'Chaldean'), and, inaccurately, "Nestorian" (a term that was originally used to refer to the Church of the East in the Sasanian Empire). The Eastern script resembles ʾEsṭrangēlā somewhat more closely than the Western script.

The Eastern script uses a system of dots above and/or below letters, based on an older system, to indicate vowel sounds not found in the script: