Semiramis (/səˈmɪrəmɪs, sɪ-, sɛ-/;^{[page needed]} Syriac: ܫܲܡܝܼܪܵܡ Šammīrām, Armenian: Շամիրամ Šamiram, Greek: Σεμίραμις, Arabic: سميراميس Samīrāmīs) was the legendary Lydian-Babylonian wife of Onnes and of Ninus, who succeeded the latter on the throne of Assyria, according to Movses Khorenatsi. Legends narrated by Diodorus Siculus, who drew primarily from the works of Ctesias of Cnidus, describe her and her relationships to Onnes and King Ninus.

Armenians and the Assyrians of Iraq, northeast Syria, southeast Turkey, and northwest Iran still use Shamiram and its derivative Samira as a given name for girls.

The real and historical Shammuramat, the original Akkadian form of the name, was the Assyrian wife of Shamshi-Adad V (ruled 824 BC–811 BC). She ruled the Neo-Assyrian Empire as its regent for five years, before her son Adad-nirari III came of age and took the reins of power. She ruled at a time of political uncertainty, which may partly explain why Assyrians may have accepted the rule of a woman when it was not allowed by their cultural tradition. She conquered much of the Middle East and the Levant and stabilized and strengthened the empire after a destructive civil war. It has been speculated that being a woman who ruled successfully may have made the Assyrians regard her with particular reverence and that her achievements may have been retold over the generations until she was gradually turned into a legendary figure.

The name of Semiramis came to be applied to various monuments in Western Asia and Anatolia whose origins had been forgotten or unknown, even the Behistun Inscription of Darius. Herodotus ascribes to her the artificial banks that confined the Euphrates. He knew her name because it was inscribed on a gate of Babylon. Various places in Mesopotamia, Media, Persia, the Levant, Anatolia, the Arabian Peninsula, and the Caucasus received names recalling Semiramis.

While the achievements of Semiramis are clearly in the realm of mythical Persian, Armenian, and Greek historiography, the historical Shammuramat certainly existed. After her husband's death, she might have served as regent for her son, Adad-nirari III. Thus, during that time Shammuramat could have been in control of the vast Neo-Assyrian Empire (911–605 BC), which stretched from the Caucasus Mountains in the north to the Arabian Peninsula in the south, and from western Iran in the east to Cyprus in the west.

In the city of Aššur on the Tigris, she had an obelisk built and inscribed that read, "Stele of Shammuramat, queen of Shamshi-Adad, King of the Universe, King of Assyria, Mother of Adad Nirari, King of the Universe, King of Assyria, Daughter-in-Law of Shalmaneser, King of the Four Regions of the World."

According to Diodorus, a first century BC Greek historian, Semiramis was of noble parents, the daughter of the fish-goddess Derketo of Ascalon and of a mortal. He related that Derketo abandoned her at birth and drowned herself. Doves fed the child until Simmas, the royal shepherd, found her. Semiramis married Onnes or Menones, a general under King Ninus, and she became an advisor to the king. Her advice led him to great successes. At the Siege of Bactra, she personally led a party of soldiers to seize a key defensive point, leading to the capture of the city.

Ninus was so struck that he fell in love with her. He tried to compel Onnes to give her to him as a wife, first offering his own daughter Sonanê in return and eventually threatening to put out his eyes as punishment. Out of fear of the king, and out of doomed passion for his wife, Onnes "fell into a kind of frenzy and madness" and hanged himself. Ninus then married Semiramis.