In Greek mythology, Nireus, son of King Charopus and Aglaea, was king of the island Syme (according to Diodorus Siculus, also of a part of Cnidia) and one of the Achaean leaders in the Trojan War. He was renowned for his outstanding beauty, being described as the second most handsome man in the Greek camp after Achilles.

Nireus was among the suitors of Helen and consequently joined in the campaign against Troy; he was said to have commanded three ships. In the military conflict with the Mysian king Telephus, which occurred on the way to Troy (during the first unsuccessful attempt to reach the city), Nireus killed Telephus' wife Hiera, who fought from a chariot "like an Amazon".

Nireus did not excel in physical strength and was eventually killed by either Eurypylus, son of Telephus, or Aeneas. However, according to the version recounted by John Tzetzes, Nireus survived the war and, together with Thoas, having been caught in the storm that scattered the Greek ships, landed first in Libya and then sailed off to Argyrinoi and the Ceraunian Mountains, where they settled near Mount Lakmynion and River Aias.