Sosylus of Lacedaemon
Sosylus of Lacedaemon was a Greek historian in the 3rd century BC. A contemporary of Hannibal, he accompanied him during the Second Punic War and is the author of the Deeds of Hannibal, a lost historical work of seven volumes; only fragments of the work are known. Sosylus taught Hannibal Greek.
It is possible that Polybios may have used material from Sosylus' history for his writing about Hannibal in The Histories.