Learchus (Greek: Λέαρχος) was an adviser in the government of the Kingdom of Cyrenaica during the reign of king Arcesilaus II.
Learchus appears to have been an early acquaintance of murder, having killed a Cyrenaean noble who was the husband of the Princess Critola and father of Queen Eryxo.
Learchus and his supporters left the city of Cyrene and created their own settlement called Barca (sometimes known as Meri, Libya).
During the construction of Barca, Learchus was able to persuade local Libyans to withdraw their allegiance from Cyrene and encourage them to come with him and to declare war on Arcesilaus.
News of Learchus and his army preceded them and reached the ears of Arcesilaus, who gathered his forces and marched to meet their opponents.
Arcesilaus and the Cyrenaean troops chased Learchus and his supporters across the country into eastern Libya unto a site called Leucon, the location of which is unknown.
Eryxo was taking counsel with her brothers and in the end asked to see Learchus and gave the impression that she wished to marry him.
This was when it was revealed that Eryxo and her brother, Polyarchus were plotting to kill Learchus in revenge for the deaths of their father, the Cyrenaean noble, and King Arcesilaus.
Demonax's reforms were disregarded by the successor to Battus, Arcesilaus III, who instigated yet another period of civil strife.