In Greek mythology, Molossus was the son of Neoptolemus and Andromache and the eponymous founder of the Molossians of Epirus. Apollodorus names him with brothers Pielus and Pergamus (the last after Troy's citadel). Through him Andromache's post-Troy fate is tied to northwestern Greece and the later Molossian royal house.
Adapted from Wikipedia, "Molossus (son of Neoptolemus)" · CC BY-SA 4.0
I.Son of Neoptolemus and Andromache
After the sack of Troy, Neoptolemus takes Andromache as captive consort. Their son Molossus becomes the mythical ancestor of the Molossian tribe of Epirus. Apollodorus' Epitome lists Molossus, Pielus, and Pergamus as the sons of that union.
The eponym links Trojan Andromache to the historical Molossian kings of Epirus, who claimed Aeacid descent through Neoptolemus' line.
II.Name note
Molossus is not to be confused with the Molossian hound breed named from the same people, nor with other post-Homeric founders. Atlas id molossus is only the mythic eponym son of Neoptolemus.