The Latin alphabet is the collection of letters originally used by the ancient Romans to write the Latin language. Largely unaltered except for a couple letters splitting (⟨J⟩ from ⟨I⟩ and ⟨U⟩ from ⟨V⟩), an addition (⟨W⟩), and extensions (such as letters with diacritics), it forms the Latin script that is used to write many languages worldwide: in western and central Europe, in Africa, in the Americas, and in Oceania.

Its basic modern 26-letter inventory is standardized as the ISO basic Latin alphabet.

The term Latin alphabet may refer to either the alphabet used to write Latin (as described in this article) or other alphabets based on the Latin script, which is the basic set of letters common to the various alphabets descended from the classical Latin alphabet, such as the English alphabet. These Latin-script alphabets may discard letters, like the Rotokas alphabet, or add new letters, like the Danish and Norwegian alphabets. Letter shapes have evolved over the centuries, including the development in Medieval Latin of lower-case, forms which did not exist in the Classical period alphabet.

The Latin alphabet evolved from the visually similar Etruscan alphabet, which evolved from the Cumaean Greek version of the Greek alphabet, which was itself descended from the Phoenician alphabet, which in turn derived from Egyptian hieroglyphs. The Etruscans ruled early Rome; their alphabet evolved in Rome over successive centuries to produce the Latin alphabet. During the Middle Ages, the Latin alphabet was used (sometimes with modifications) for writing Romance languages, which are direct descendants of Latin, as well as for writing Celtic, Germanic, Baltic and some Slavic languages. With the age of colonialism and Christian evangelism, the Latin script spread beyond Europe, coming into use for writing indigenous American, Australian, Austronesian, Austroasiatic and African languages. More recently, linguists have also tended to prefer the Latin script or the International Phonetic Alphabet (itself largely based on the Latin script) when transcribing or creating written standards for non-European languages, such as the African reference alphabet.

Although Latin did not use diacritical marks, apart from the apex and sicilicus, signs of truncation of words (often placed above or at the end of the truncated word) were very common. Furthermore, abbreviations or smaller overlapping letters were often used. This meant that if the text was engraved on stone, the number of letters to be engraved was reduced, while if it was written on paper or parchment, it saved precious space. This custom continued in the Middle Ages: hundreds of symbols and abbreviations exist, varying from century to century.

It is generally believed that the Latin alphabet used by the Romans was derived from the Old Italic alphabet used by the Etruscans. That alphabet was derived from the Euboean alphabet used by the Cumae, which in turn was derived from the Phoenician alphabet.

Latin included 21 different characters. The letter ⟨C⟩ was the western form of the Greek gamma, but it was used for the sounds /ɡ/ and /k/ alike, possibly under the influence of Etruscan, which might have lacked any voiced plosives. Later, probably during the 3rd century BC, the letter ⟨Z⟩ – not needed to write Latin properly – was replaced with the new letter ⟨G⟩, a ⟨C⟩ modified with a small vertical stroke, which took its place in the alphabet. From then on, ⟨G⟩ represented the voiced plosive /ɡ/, while ⟨C⟩ was generally reserved for the voiceless plosive /k/. The letter ⟨K⟩ was used only rarely, in a small number of words such as Kalendae, often interchangeably with ⟨C⟩.

After the Roman conquest of Greece in the 1st century BC, Latin adopted the Greek letters ⟨Y⟩ and ⟨Z⟩ (or readopted, in the latter case) to write Greek loanwords, placing them at the end of the alphabet. An attempt by the emperor Claudius to introduce three additional letters ⟨Ↄ, Ⅎ, Ⱶ⟩ did not last. Thus it was during the classical Latin period that the Latin alphabet contained 21 letters and 2 foreign letters: