A trigraph (from the Greek: τρεῖς, treîs, "three" and γράφω, gráphō, "write") is a group of three letters used to represent a single sound or a combination of sounds that does not correspond to the written letters combined. For example, in the word schilling, the trigraph sch represents the voiceless postalveolar fricative /ʃ/, rather than the consonant cluster */skh/. In the word beautiful, the sequence eau is pronounced /juː/, and in the French word château it is pronounced /o/. It is sometimes difficult to determine whether a sequence of letters in English is a trigraph, because of the complicating role of silent letters. There are few productive trigraphs in English; one is tch as in watch.

The trigraph sch is German, where it is equivalent to the English sh; like English sh, it is not regarded as an independent letter of the alphabet. In Hungarian, the trigraph dzs is treated as a distinct letter, with its own place in the alphabet. It is pronounced like an English "j" /dʒ/. The combination gli in Italian can also be a trigraph, representing the palatal lateral approximant /ʎ/ before vowels other than i.

A trigraph (from the Greek forms tri- = three and graph- = write) is a group of three symbols, most commonly letters.

Trigraph can mean: