Belus or Belos in classical Greek or classical Latin texts (and later material based on them) in a Assyrian context refers to one or another purportedly ancient and historically nonexistent Assyrian king, such king in part at least an euhemerization of the Babylonian god Bel Marduk.

Belus most commonly appears as the father of Ninus who otherwise mostly appears as the first known Assyian king. Ctesias provides not information about Ninus' parentage. But already in Herodotus we find a Ninus son of Belus among the ancestors of the Heraclid dynasty of Lydia though here Belus is strangely and uniquely made a grandson of Heracles. See Omphale for discussion.

A fragment by Castor of Rhodes preserved only in the Armenian translation of Eusebius of Caesarea makes Belus king of Assyria at the time when Zeus and the other gods fought first the Titans and then the giants. Castor says Belus was considered a god after his death but that he does not know how many years Belus reigned.

Belus elsewhere is a vague, ancestral figure.

In those versions of the tale of Adonis which make Adonis the son of Theias or Thias the King of Assyria, this Theias or Thias is the son of Belus.

Ovid's Metamorphoses (4.212f) speaks of King Orchamus who ruled the Achaemenid cities of Persia as the 7th in line from ancient Belus the founder. But no other extent sources mentions either Orchamus or his daughters Leucothoe and Clytie.

Nonnus in his Dionysiaca (18.5f) brings in King Staphylus of Assyria and his son Botrys who entertain Dionysus, characters unknown elsewhere. Staphylus claims to be grandson of Belus.

Diodorus Siculus (6.5.1) introduces the Roman god Picus (normally son of Italy and calls him brother of Ninus (and therefore perhaps son of Belus).

The odd connection between Picus and Ninus reappears in John of Nikiû's Chronicle (6.2f) which relates that Cronus was the first king of Assyria and Persia, that he married an Assyrian woman named Rhea and that she bore him Picus (who was also called Zeus) and Ninus who founded the city of Ninus (Nineveh). Cronus removed to Italy but was then slain by his son Zeus Picus because he devoured his children. Then Zeus became the father of Belus by his own sister. After the disappearance of Zeus Picus (who apparently reigned over both Italy and Assyria), Belus son of Zeus Picus succeeded to the throne in Assyria (and we later find Faunus who is elswhere always the son of Picus reigning in Italy before moving to Egypt and turning into Hermes Trismegistus father of Hephaestus!). Upon the death of Belus, his uncle Ninus became king and then married his own mother who was previouly called Rhea but is now reintroduced under the name of Semiramis. It is explained that from that time on this custom was maintained so that Persians think nothing of taking a mother or sister or daughter as a wife.

Later historians and chronographers make no mention of such stories. They either do not mention Belus at all or accept him as father of Ninus. They also dispute as to whether the Biblical Nimrod was the same as Belus or the father of Belus or a more distant ancestor of Belus.

It is likely that this Assyrian Belus should mostly not be distinguished from the euhemerized Bablyonian Belus. But some chronographers make a distinction between them. See Belus (Babylonian).

See also Bel (god) and Ba‘al.