Which Assyrian king's library contained the most complete copy of the Epic?

The most complete surviving copy of the Epic of Gilgamesh was found in the library of the Assyrian king Ashurbanipal. The library stood at Nineveh, the capital of the Neo-Assyrian Empire, and preserved thousands of clay tablets and fragments.

Ashurbanipal ruled from 668 to about 627 BCE and was unusual among ancient kings for presenting himself as a learned reader and scholar. He ordered scribes to collect, copy, and organize works from across Mesopotamia, including Babylonian literary traditions. The Gilgamesh tablets discovered there became the foundation for modern knowledge of the Standard Babylonian version.

The copy is not perfectly complete: many tablets are damaged, and gaps remain. Scholars reconstruct missing passages by comparing fragments from other sites and earlier versions. The library’s importance therefore lies not only in preserving Gilgamesh but also in safeguarding myths, rituals, lexical lists, scientific texts, and historical records. Hammurabi, Nebuchadnezzar, and Sargon were important Mesopotamian rulers, but they are not the answer to this library question.