In the theatre of ancient Greece, the choregos (pl. choregoi; Greek: χορηγός, Greek etymology: χορός "chorus" + ἡγεῖσθαι "to lead") was a wealthy Athenian citizen who assumed the public duty, or choregiai, of financing the preparation for the chorus and other aspects of dramatic production that were not paid for by the government of the polis or city-state. Modern Anglicized forms of the word include choragus and choregus, with the accepted plurals being the Latin forms choregi and choragi. In Modern Greek, the word χορηγός is synonymous with the word "grantor".

Choregoi were appointed by the archon and the tribes of Athenian citizens from among the Athenian citizens of great wealth. Service as a choregos, though an honor, was a duty for wealthy citizens and was part of the liturgical system designed to improve the city-state's economic stability through the use of private wealth to fund public good. Choregoi paid for costumes, rehearsals, expenses of the chorus (including training, salaries, board and lodging), scenery, props (including elaborate masks), special effects and most of the musicians. The choregos also hosted a feast if his chorus proved victorious in competition. The prizes for drama at the Athenian festival competitions were awarded jointly to the playwright and the choregos. Such victories carried prestige for the choregos. Several notable political figures served as choregoi, including Themistocles, Pericles and Plato, among others. Monuments were built in honor of victorious choregoi.

At the turn of the 17th century AD, in an attempt to recreate the ancient Greek dramatic tradition, the position was revived briefly in Italian opera, and combined the roles of impresario and director.

Under the Athenian constitution, choregoi were appointed by the archon and the tribes of Athenian citizens. The archon appointed choregoi for the tragedies, while the tribes supplied five choregoi for the comedies as well as choregoi for the Dionysia and Thargelia (the major festival competitions). The archon, who began this process months in advance of a festival, were able easily to identify potential dramatic choregoi because their mutual wealth allowed them to move in the same social circles as the most qualified candidates. In order to be considered for the role of choregos, an individual had to be an Athenian citizen and possess great wealth. Choregoi for choruses of boys were required by Athenian law to be over forty years old to protect the young participants. Volunteers from this selected group of qualified individuals may have been the source of most appointments. The figure of the choregos can be traced back as early as the 7th century B.C. References to the title are found in recovered portions of the earliest choral lyric poetry, including the Parthenia (or "Maiden-songs") of Alkman, a poet of archaic Sparta.

Service as a choregos, though an honor, was a duty rather than a choice for wealthy citizens. This duty was one among many built into the state liturgical system of ancient Athens, which was designed to improve the city-state's economic stability through the use of private wealth to fund public good. Once nominated, however, a potential choregos had three choices. He could accept the nomination and the duty. Through a process called skepsis, he could claim one of several specifically defined exemptions and be excused from service. Finally, he could identify another Athenian who was more qualified to perform the role of choregos and use the procedure of skepsis to resolve the matter.

Choregoi were responsible for supporting many aspects of theatre production in ancient Athens: paying for costumes, rehearsals, the chorus, scenery or scene painting (including such items as mechane and ekkyklema), props (including elaborate masks), special effects, such as sound, and musicians, except that the state provided the flute player and paid the actors not in the chorus. At the City Dionysia in Athens, for example, the choregos was expected to finance all aspects relating to the chorus, which could include training, the hiring of an expert to execute such training, salaries, and board and lodging during a lengthy rehearsal period.

The choregos did not act as the director for the production; this role was fulfilled by the playwright. The choregos would appoint a chorodidaskalos (Χοροδιδάσκαλος, often shortened to διδάσκαλος), often the playwright, to train the chorus. The choregos was often expected to host a feast, analogous to a modern cast party, should his chorus prove victorious in competition. According to the Oxford Dictionary of the Classical World: "The sums spent on choregiai show that the duty could elicit vast expenditure. One extremely enthusiastic choregos catalogues a list which represents an outlay of nearly two and a half talents. This includes a dithyrambic choregia at the Little Panathenaea for 300 drachmae, and a tragic choregia for 3,000 dr. The latter figure is roughly ten times what a skilled worker might have earned annually." The reorganization of the choregia in 406 BC spread the cost among the wider community – the synchoregia – with the choregos paying only part of the expense.

The word choregoi was also applied to men who performed certain cultic duties regulating the choruses of women in ritual contexts, such as with the cult of Auxesia.