Gaj's Latin alphabet (Serbo-Croatian: Gajeva latinica / Гајева латиница, pronounced [ɡâːjeva latǐnit͡sa]), also known as abeceda (Serbian Cyrillic: абецеда, pronounced [abet͡sěːda]) or gajica (Serbian Cyrillic: гајица, pronounced [ɡǎjit͡sa]), is the form of the Latin script used for writing all four standard varieties of Serbo-Croatian: Bosnian, Croatian, Montenegrin, and Serbian. It contains 27 individual letters and 3 digraphs. Each letter (including digraphs) represents one Serbo-Croatian phoneme, yielding a highly phonemic orthography. It closely corresponds to the Serbian Cyrillic alphabet.

The alphabet was initially devised by Croatian linguist Ljudevit Gaj in 1835 during the Illyrian movement in ethnically Croatian parts of the Austrian Empire. It was largely based on Jan Hus's Czech alphabet and was meant to serve as a unified orthography for three Croat-populated kingdoms within the Austrian Empire at the time, namely Croatia, Dalmatia and Slavonia, and their three dialect groups, Kajkavian, Chakavian and Shtokavian, which historically utilized different spelling rules. The alphabet's final form was defined in the late 19th century.

A slightly reduced version is used as the alphabet for Slovene, and a slightly expanded version is used for modern standard Montenegrin. A modified version is used for the romanization of Macedonian. It further influenced alphabets of Romani languages that are spoken in Southeast Europe, namely Vlax and Balkan Romani.

Latin is designated as a "script in official use", with Serbian Cyrillic having the constitutional status of "official script". However, in media and everyday life, latin is used more.

The alphabet consists of thirty upper and lower case letters:

Letters are referred to by their name: a, be, ce, če, će, de, dže, đe, e, ef, ge, ha, i, je, ka, el, elj, em, en, enj, o, pe, er, es, eš, te, u, ve, ze, že, or, in the case of consonants, by being appended by schwa, e.g. /fə/. In mathematics, ⟨j⟩ is commonly pronounced jot, as in the German of Germany.^{[citation needed]}

Various foreign letters are utilised in orthographically unadapted loanwords and foreign proper names, such as Québec. Orthographically unadapted spelling of foreign names and some loanwords is standard in Croatia, whereas Serbians prefer to use orthographically adapted spellings. Non-native letters Q, W, X, and Y appear on the Serbo-Croatian keyboard. These four letters are usually named as follows: ⟨q⟩ as kve or ku, ⟨w⟩ as duplo ve or dvostruko ve, ⟨x⟩ as iks, and ⟨y⟩ as ipsilon.

Digraphs ⟨dž⟩, ⟨lj⟩ and ⟨nj⟩ are considered to be single letters, and they signify single phonemes. However, they are distinguished from occurrences of two such letters that signify two distinct phonemes: džep (/d͡ʒêp/, Cyrillic џеп) uses the digraph, while nadživjeti (/nadʒǐːvjeti/, Cyrillic надживјети, morphological boundary: prefix nad- + base živjeti) uses two separate letters.