Celestial divination emerged within a cuneiform scribal tradition devoted to the systematic reckoning of “signs,” taken as messages from the gods as to what lay in store for humanity. The technique of divining the future in this way lay in the methods of scholarship involved in the copying, consulting, and commenting on lists of omens. This was evidently conceived of as categorically different from the direct reception of the gods' message through visions, frenzy, or dream incubation. Since the end of the second millennium b.c., the reading and the interpretation of heavenly signs in some form or another are well attested in Mesopotamia, and the spread of this tradition is already well evidenced in states influenced by the cuneiform literate culture, such as the Hittite Empire, Syria, and Elam, which bordered Mesopotamia. Textual evidence for the history of Babylonian divination from celestial signs, attestation of this activity in Mari letters notwithstanding, can be defined as beginning with late Old Babylonian omen texts and continuing through Middle Babylonian and Middle Assyrian forerunners to the canonical celestial omen series Enūma Anu Enlil to the variety of celestial and nativity omens as well as horoscopes of the Achaemenid, Seleucid, and Arsacid periods. Over the course of this nearly 2,000-year-long history, changes and developments certainly occurred. But despite changes in textual formalities and even specific content and methods, the coherence of Babylonian astrology may be found in the persistent belief that the sky could be read as symbolic for the human realm, as expressed in the metaphor of the heavenly writing.