Heta is a conventional name for the historical Greek alphabet letter Eta (Η) and several of its variants, when used in their original function of denoting the consonant /h/. The letter Η had been adopted by Greek from the Phoenician letter Heth () originally with this consonantal sound value, and Hēta was its original name. The Italic alphabets, and ultimately Latin, adopted the letter H from this Greek usage. However, Greek dialects progressively lost the sound /h/ from their phonological systems. In the Ionic dialects, where this loss of /h/ happened early, the name of the letter naturally changed to Ēta, and the letter was subsequently turned from a consonant to a new use as a vowel, denoting the long half-open /ɛː/ sound. In this function it later entered the classical orthography adopted across the whole of Greece. According to traditional accounts, the new vowel, Ēta, was originally the innovation of the poet Simonides of Ceos (556-468 BC).
In dialects that still had the /h/ sound as part of their phonological systems, including early Athens, the same letter continued to be used in its consonantal function. Just like vocalic Eta, it could occur in a number of glyph variants in different local varieties of the alphabet, including one shaped like a square "8" similar to the original Phoenician (), but also a plain square (), a crossed square (), shapes with two horizontal () or with diagonal bars ().