in Roman legend, son of the hero Aeneas and the traditional founder of Alba Longa, probably the site of the modern Castel Gandolfo, near Rome. In different versions, Ascanius is placed variously in time. The usual account, found in Virgil's Aeneid, makes the Trojan Creusa his mother. After the fall of Troy, Ascanius and Aeneas escaped to Italy. Ascanius set off a war between the Trojans and the Latins by wounding the pet stag of Silvia, the daughter of the royal herdsman. Aeneas won the war, slew the Latin commander, Turnus, and married Lavinia, the daughter of King Latinus (Latinus). Aeneas subsequently founded Lavinium, the parent city of Alba Longa and Rome. Ascanius became king of Lavinium after his father's death. Thirty years after Lavinium was built, Ascanius founded Alba Longa and ruled it until he died.

In the Roman historian Livy's account, however, Ascanius was born after the founding of Lavinium and was the son of Aeneas and Lavinia. Ascanius was also called Iulus, and through him by that name the gens Julia (including the family of Julius Caesar (Caesar, Julius)) traced its descent.