The origin of Georgia’s unique alphabet is controversial. Whereas the Greek and Latin alphabets are the results of slow and gradual transformations of older scripts (rather than deliberate creations), the Georgian alphabet shows up in history out of nowhere. This makes it plausible that it was invented, either by one person or several. So the question is: who created it?
Historical tradition gives two conflicting answers. The first comes from a medieval Georgian chronicle called “The Lives of the Kings of Kartli.” It tells of Parnavaz, the first Kartlian king, who reigned in the third century BC. Among other exploits, the chronicle says that Parnavaz devised the Georgian “script” (მწიგნობრობა, mtsignobroba). Some have interpreted this to mean that he developed the Georgian alphabet, but mtsignobroba can also mean “literacy.” This literacy could have been literacy in the Georgian alphabet, but more likely it was literacy in the Aramaic alphabet, which at the time was the script of the Persians. This is confirmed by archeology, which has found pre-Christian traces of the Aramaic alphabet in Georgia, but none of the Georgian.
The second traditional answer is that the Georgian alphabet was invented in the fourth century AD by an Armenian priest named Mesrop Mashtots, the same person who invented the Armenian alphabet. This oft-repeated claim, found in a fifth century hagiography of Mashtots, is supported by graphical similarities between several characters of the Armenian and Georgian alphabets. However, it is suspect for several reasons. For one thing, the entire passage containing the story may well have been added at a much later date, in which case it may be fabricated. Supposing the story is part of the original history, it is not independently corroborated by any other historical source—Armenian, Georgian, or otherwise. This is a problem when dealing with a story in which the author has motive to make up (for instance, to make Mashtots and thereby Armenia seem more glorious). Besides this, the story also has it that Mashtots needed an interpreter to spread his newly-created alphabet to the Georgians, but it’s unrealistic to imagine that an alphabet with such a tight letter-to-sound correspondence as the Georgian one could have been created by someone without a masterful command of the language. All of this is to say that there’s very little reason to believe that Mashtots was the inventor of the Georgian alphabet.
So if it wasn’t him and it wasn’t Parnavaz, then who was it? Here things become speculative. It could be that the story about Mashtots is not a lie but an exaggeration, and Mashtots was a part of or a consultant to the team of scholars that created the Georgian alphabet. The alphabet almost certainly came about in connection with the spread of Christianity in Georgia, but that doesn’t narrow things down much. Georgian Christians could have made the alphabet to bring religion to their compatriots, or it could have been made by foreign missionaries, the way Cyril and Methodius and their followers made alphabets for the Slavs. We can safely assume that whoever invented it was fully literate in at least one major foreign language, but experts can’t even agree on whether it was Greek, Aramaic, or something else. In short, very little is known.
Actually, all of this truly relates only to the ancient Georgian alphabet (asomtavruli), which is distinct from the modern one (mkhedruli). The question of how the modern alphabet came about is much less speculative than the question of how the ancient one came about. It will suffice to say that the modern alphabet derives ultimately from a cursive form of the ancient.