Akshak (Sumerian: 𒌔𒆠, akšak) (pre-Sargonic - u4kúsu.KI, Ur III - akúsu.KI, Phonetic - ak-su-wa-ak) was a city of ancient Sumer, situated on the northern boundary of Akkad, sometimes identified with Babylonian Upi (Greek Opis).

Puzur-Nirah is also mentioned in the millennia later literary composition Weidner Chronicle as reigning in Akshak when a female tavern-keeper, Kug-bau of Kish, was appointed overlordship over Sumer.

[6] Following this, Akshak was at war with Lagash, and was captured by Eannatum, who claims in one inscription (on Boulder A v 4-5) to have smitten its king, Zuzu.

Classical writers located it where the Tigris and Euphrates rivers are closest together and it was mentioned along with Kish and Girsu in early records.

Surveyed sites marked as possible locations of Akshak were Tell Mohammad, Tell Rishad, and Tell Abu Jawan.

[19] Tulul Mujaili' (also Tulül al-Mugeli' and el-Mjel'aat), which lies 15 kilometers northeast of Cteshiphon, has also been suggested as Akshak and also Opis.

A surface survey showed occupation in Early Dynastic through Neo-Babylonian periods, mainly beginning in Kassite times.

[21] Based on an early geographical list the site of Tell Sinker (N 56 ̧24' and E 44 ̧14'), on ancient bed of the Tigris river northwest of Baghdad, has also been proposed.