Who is the traditional author of the Standard Babylonian version?

The traditional author of the Standard Babylonian version is Sîn-lēqi-unninni.

He was a Babylonian exorcist-priest, or mašmaššu, probably active between about 1300 and 1000 BCE. Later literary catalogues associate him with the most complete and influential form of the Akkadian Epic of Gilgamesh. Scholars usually describe him more cautiously as a compiler or editor rather than an author in the modern sense, because the poem developed from older Sumerian and Akkadian traditions.

The edition linked with Sîn-lēqi-unninni is known by its opening words, ša nagba īmuru, meaning “He who saw the deep.” It includes the famous account of Utnapishtim and the Flood in Tablet XI. The surviving text is not a single intact manuscript: the standard version is reconstructed from many fragmentary tablets, especially copies from the seventh-century BCE Library of Ashurbanipal at Nineveh.

A common mix-up is to treat Sîn-lēqi-unninni as the historical author of every Gilgamesh story. Earlier poems about Gilgamesh circulated for centuries, and his precise historical existence is uncertain. Later Uruk intellectual families even claimed Sîn-lēqi-unninni as an ancestor, suggesting that his reputation became partly legendary.