Astrology is a belief in a relation between celestial observations and terrestrial events. People made conscious attempts to measure, record, and predict seasonal changes by reference to astronomical cycles . Early evidence of such practices appears as markings on bones and cave walls, which show that the lunar cycle was being noted as early as 25,000 years ago; the first step towards recording the Moon's influence upon tides and rivers, and towards organizing a communal calendar. With the Neolithic Revolution new needs were also being met by the increasing knowledge of constellations, whose appearances in the night-time sky change with the seasons, thus allowing the rising of particular star-groups to herald annual floods or seasonal activities. By the 3rd millennium BCE, widespread civilisations had developed sophisticated understanding of celestial cycles, and are believed to have consciously oriented their temples to create alignment with the heliacal risings of the stars.

There is scattered evidence to suggest that the oldest known astrological references are copies of texts made during this period, particularly in Mesopotamia. Two, from the Venus tablet of Ammisaduqa (compiled in Babylon round 1700 BC) are reported to have been made during the reign of king Sargon of Akkad (2334–2279 BC). Another, showing an early use of electional astrology, is ascribed to the reign of the Sumerian ruler Gudea of Lagash (c. 2144–2124 BC). However, there is controversy over whether they were genuinely recorded at the time or merely ascribed to ancient rulers by posterity. The oldest undisputed evidence of the use of astrology as an integrated system of knowledge is attributed to records that emerge from the first dynasty of Mesopotamia (1950–1651 BC).

Among West Eurasian peoples, the earliest evidence for astrology dates from the 3rd millennium BC, with roots in calendrical systems used to predict seasonal shifts and to interpret celestial cycles as signs of divine communications. Until the 17th century, astrology was considered a scholarly tradition, and it helped drive the development of astronomy. It was commonly accepted in political and cultural circles, and some of its concepts were used in other traditional studies, such as alchemy, meteorology and medicine. By the end of the 17th century, emerging scientific concepts in astronomy, such as heliocentrism, undermined the theoretical basis of astrology, which subsequently lost its academic standing and became regarded as a pseudoscience. Empirical scientific investigation has shown that predictions based on these systems are not accurate.

In the 20th century, astrology gained broader consumer popularity through the influence of regular mass media products, such as newspaper horoscopes.

Babylonian astrology is the earliest recorded organized system of astrology, arising in the 2nd millennium BC. There is speculation that astrology of some form appeared in the Sumerian period in the 3rd millennium BC, but the isolated references to ancient celestial omens dated to this period are not considered sufficient evidence to demonstrate an integrated theory of astrology. The history of scholarly celestial divination is therefore generally reported to begin with late Old Babylonian texts (c. 1800 BC), continuing through the Middle Babylonian and Middle Assyrian periods (c. 1200 BC).

By the 16th century BC the extensive employment of omen-based astrology can be evidenced in the compilation of a comprehensive reference work known as Enuma Anu Enlil. Its contents consisted of 70 cuneiform tablets comprising 7,000 celestial omens. Texts from this time also refer to an oral tradition – the origin and content of which can only be speculated upon. At this time Babylonian astrology was solely mundane, concerned with the prediction of weather and political matters, and prior to the 7th century BC the practitioners' understanding of astronomy was fairly rudimentary. Astrological symbols likely represented seasonal tasks, and were used as a yearly almanac of listed activities to remind a community to do things appropriate to the season or weather (such as symbols representing times for harvesting, gathering shell-fish, fishing by net or line, sowing crops, collecting or managing water reserves, hunting, and seasonal tasks critical in ensuring the survival of children and young animals for the larger group). By the 4th century, their mathematical methods had progressed enough to calculate future planetary positions with reasonable accuracy, at which point extensive ephemerides began to appear.

Babylonian astrology developed within the context of divination. A collection of 32 tablets with inscribed liver models, dating from about 1875 BC, are the oldest known detailed texts of Babylonian divination, and these demonstrate the same interpretational format as that employed in celestial omen analysis. Blemishes and marks found on the liver of the sacrificial animal were interpreted as symbolic signs which presented messages from the gods to the king.

The gods were also believed to present themselves in the celestial images of the planets or stars with whom they were associated. Evil celestial omens attached to any particular planet were therefore seen as indications of dissatisfaction or disturbance of the god that planet represented. Such indications were met with attempts to appease the god and find manageable ways by which the god's expression could be realised without significant harm to the king and his nation. An astronomical report to the king Esarhaddon concerning a lunar eclipse of January 673 BC shows how the ritualistic use of substitute kings, or substitute events, combined an unquestioning belief in magic and omens with a purely mechanical view that the astrological event must have some kind of correlate within the natural world: