Long i ( or [littera] i longa), written , is a variant of the letter i found in ancient and early medieval forms of the Latin script.
In inscriptions dating to the early Roman Empire, it is used frequently but inconsistently to transcribe the long vowel . In Gordon's 1957 study of inscriptions, it represented this vowel approximately 4% of the time in the 1st century CE, then 22.6% in the 2nd century, 11% in the 3rd, and not at all from the 4th century onward, reflecting a loss of phonemic vowel length by this time (one of the phonological changes from Classical Latin to Proto-Romance). In this role it is equivalent to the (also inconsistently-used) apex, which can appear on any long vowel: . An example would be , which is generally spelled today, using macrons rather than apices to indicate long vowels. On rare occasions, an apex could combine with long i to form , e.g. .
The long i could also be used to indicate the semivowel [j], e.g. or , the latter also , pronounced . It was also used to write a close allophone of the short i phoneme, used before another vowel, as in , representing .
Later on in the late Empire and afterwards, in some forms of New Roman cursive, as well as pre-Carolingian scripts of the Early Middle Ages such as Visigothic or Merovingian, it came to stand for the vowel in word-initial position. For example, , which would be in modern spelling.
The character exists in Unicode as U+A7FE , , having been suggested in a 2006 proposal.