Sîn-šumu-līšir or Sîn-šumu-lēšir (Neo-Assyrian cuneiform: or , meaning "Sîn, make the name prosper!"), also spelled Sin-shum-lishir, was a usurper king in the Neo-Assyrian Empire, ruling some cities in northern Babylonia for three months in 626 BC during a revolt against the rule of the king Sîn-šar-iškun. He was the only eunuch to ever claim the throne of Assyria. Nothing is known of Sîn-šumu-līšir's background or family and he first appears as a prominent courtier and general in the reign of Aššur-etil-ilāni (631–627 BC). After the death of Aššur-etil-ilāni's father and predecessor Ashurbanipal (669–631 BC), Sîn-šumu-līšir was instrumental in securing Aššur-etil-ilāni's rise to the throne and consolidating his position as king by defeating attempted revolts against his rule. It is possible that Sîn-šumu-līšir, as a prominent general close to the king, was the de facto ruler of Assyria throughout Aššur-etil-ilāni's reign. Aššur-etil-ilāni died in 627 BC after a very short reign and in the following year, Sîn-šumu-līšir rebelled against Aššur-etil-ilāni's brother and successor Sîn-šar-iškun, possibly due to feeling that his prominent position was threatened by the rise of the new king. Sîn-šumu-līšir successfully seized cities such as Nippur and Babylon but was defeated by Sîn-šar-iškun after just three months. Nothing is known of Sîn-šumu-līšir's background or family. He was a eunuch and probably already a prominent courtier during the reign of Ashurbanipal (r. 669–631 BC). Eunuchs had often been appointed to prominent government positions in the Assyrian Empire because they could have no dynastic aspirations and thus in the mind of the Assyrians could not represent potential threats. After Ashurbanipal's death, Sîn-šumu-līšir played a key role in securing the rise of his son Aššur-etil-ilāni to the throne, probably with the aid of his own private soldiers. Sîn-šumu-līšir is then first mentioned in Assyrian sources as the (great/chief eunuch) of Aššur-etil-ilāni.