Illyrian religion refers to the religious beliefs and practices of the Illyrian peoples, a group of tribes who spoke the Illyrian languages and inhabited part of the western Balkan Peninsula from at least the 8th century BC until the 7th century AD. The available written sources are very tenuous. They consist largely of personal and place names, and a few glosses from Classical sources.

Still insufficiently studied, the most numerous traces of religious practices of the pre-Roman era are those relating to religious symbolism. Symbols are depicted in every variety of ornament and reveal that the chief object of the prehistoric cult of the Illyrians was the Sun, worshipped in a widespread and complex religious system. The Illyrian Sun-deity is figuratively represented on Iron Age plaques as the god of the sky and lightning, also associated with the fire altar where he throws lightning bolts. Illyrian deities were mentioned in inscriptions on statues, monuments, and coins of the Roman period, and some interpreted by Ancient writers through comparative religion. To these can be added a larger body of inscriptions from the south-eastern Italian region of Apulia written in the Messapic language, which is generally considered to be related to Illyrian, although this has been debated as mostly speculative. There appears to be no single most prominent god for all the Illyrian tribes, and a number of deities evidently appear only in specific regions.

As pagans, Illyrians believed in supernatural powers and they attributed to the deities qualities that were reflected in everyday life, health and disease, natural abundance and natural disaster. A number of Illyrian toponyms and anthroponyms derived from animal names and reflected the beliefs in animals as mythological ancestors and protectors. The serpent was one of the most important animal totems. Illyrians believed in the force of spells and the evil eye, in the magic power of protective and beneficial amulets which could avert the evil eye or the bad intentions of enemies. The rich spectrum in religious beliefs and burial rituals that emerged in Illyria, especially during the Roman period, may reflect the variation in cultural identities in this region.

Certain aspects of the deities and beliefs of the Illyrians stem ultimately from Proto-Indo-European mythology. Alongside the Thracian and Dacian beliefs, it constitutes part of Paleo-Balkan mythologies. Albanians preserved traces of Illyrian religious symbolism, and ancient Illyrian religion is one of the underlying sources from which Albanian folk beliefs have drawn nourishment. One can also find several traces of Illyrian cults in the religious and superstitious beliefs among south Slavic peoples today.

Cults from the Neolithic tradition—especially those that were associated with the fertility of the earth and with agriculture in general—continued to be practised throughout the Bronze Age and at the beginning of the Iron Age in the Western Balkans. Those traditions included the cult of the Earth Mother, the cult of the sun, and the cult of the serpent. During the early Iron Age, the Illyrian art was geometric and non-representational, with the combination of concentric circles, rhomboids, triangles and broken lines. It was a severe type of art devoid of fantasy, intended for farmers and cattle breeders or warriors. The absence of figured ornament may reflect an apparent lack of anthropomorphic cults during the early Iron Age. The geometric art of the period, which reached its climax in the 8th century BC, seems to be the only common feature between the different Illyrian areas, as artistic ornaments found after the 6th century BC rather show an outside influence, mainly from archaic Greece and Etruscan Italy.

Archaeological evidence demonstrate the existence of two main cults based upon two roughly defined geographic criteria: the cult of the serpent appears to have occurred principally in the southern regions of Illyria, while the waterfowl and solar symbols predominated in the north. The serpent as the symbol of fertility, protector of the hearth and a chthonic animal, could also be connected with the cult of the sun.

Many of the symbols found throughout Illyria were associated with the Sun, suggesting that the Sun worship was a cult common to Illyrian tribes. Early figurative evidence of the celestial cult in Illyria is provided by 6th century BCE plaques from Lake Shkodra, which belonged to the Illyrian tribal area of what was referred in historical sources to as the Labeatae in later times. Each of those plaques portray simultaneously sacred representations of the sky and the sun, and symbolism of lightning and fire, as well as the sacred tree and birds (eagles). In those plaques there is a mythological representation of the celestial deity: the Sun deity animated with a face and two wings, throwing lightning bolts into a fire altar, which in some plaques is held by two men (sometimes on two boats).

The solar deity was often depicted by Illyrians as an animal figure, the likes of the birds, serpents and horses, or represented geometrically as a spiral, a concentric circle or a swastika. The latter, moving clockwise (卍), portrayed the solar movement. Several bronze pendants widespread in the region have the shape of solar symbols such as a simple disk without rays, with four rays which form a cross, and with more rays. There are pendants that have more circles placed concentrically from the center to the periphery. Maximus of Tyre (2nd century AD) reported that the Paeonians worshipped the sun in the form of a small round disk fixed on the top of a pole. The sun-disk fixed on the top of a pole is also depicted in the coins of the Illyrian city of Damastion. Among the Liburnians and the Veneti, the sun-disk is depicted as a sun-boat borne across the firmament.