The siege of Himera (480 BC) was the first military action of the Carthaginian invasion of Sicily of 480, and was ended by the dramatic Carthaginian defeat at the battle of Himera.
The Carthaginian army landed at Parnormus on the northern coast of Sicily. According to the ancient sources the army was 300,000 strong, and was led by one of many Hamilcars to appear in Carthaginian history. After three days of rest Hamilcar led his army east along the coast towards the city of Himera, marching alongside the fleet. According to Herodotus the Carthaginians had come to Sicily to help Terillus, the exiled former tyrant of Himera and this line of march would fit with that story. When he reached the city Hamilcar built two camps, both on the western side of Himera. The first, on the coast, was protected by a deep ditch and a wooden palisade. Most of his ships were beached in this camp. The second camp, stretched from the navy camp all the way to some hills close to the city.
The city was defended by its own army, and close by was the army of Theron, ruler of Akragas, the man who had expelled Terillus in the first place. After building his camps Hamilcar advanced towards the city. The defenders came out to fight and suffered a heavy defeat. Theron does not appear to have been involved in this battle. In the aftermath of the battle outside the city Theron sent messengers to Gelon, Tyrant of Syracuse, asking for his help. Gelon had already mobilised his army, and advanced towards the city at the head of 50,000 infantry and 5,000 cavalry (according to Diodorus). As with the Carthaginian army this is probably an exaggeration, but even so the combined armies of Gelon, Theron and Himera were still outnumbered.
After arriving close to Himera, Gelon built his own camp, fortified with a ditch and palisade. He used his cavalry to capture a large number of Carthaginian straggles who had been looting the countryside. These successes restored morale in Himera, and gates that had been blocked in preparation for a Carthaginian assault were re-opened to prepare for a Greek offensive.
After these early successes Gelon decided to attack the Carthaginian naval camp, hoping to destroy their fleet and kill Hamilcar, who was expected to be in the camp preparing for a sacrifice. The resulting battle of Himera was a crushing Greek victory. Hamilcar was killed and most of his army destroyed. The siege was lifted, and the Carthaginians didn't campaign on Sicily for another eighty years.