Masada (Hebrew: מְצָדָה məṣādā, 'fortress'; Arabic: جبل مسعدة) is a mountain-top fortress complex in the Judaean Desert, overlooking the western shore of the Dead Sea in southeastern Israel. The fort, built in the first century BCE, was constructed atop a natural plateau rising over 400 m (1,300 ft) above the surrounding terrain, 20 km (12 miles) east of modern Arad.

The most significant remains at the site date to the reign of Herod the Great, King of Judaea c. 37–4 BCE, who transformed Masada into a fortified desert refuge early in his rule. He enclosed the summit with a casemate wall and towers, and constructed storerooms, an advanced water system, and bathhouses, along with two elaborate palaces: one on the western side and another built across three terraces on the northern cliff. These palaces remain among the finest examples of Herodian architecture.

Masada is most renowned for its role during the First Jewish–Roman War (66–73 CE), when it became the final holdout of Jewish rebels following the destruction of Jerusalem. A group known as the Sicarii, led by Eleazar ben Ya'ir, defended the site against the Roman Tenth Legion under Lucius Flavius Silva. The Romans laid siege by building a circumvallation wall and a massive ramp. According to Josephus, when the walls were breached in 73/74 CE, the Romans found nearly 1,000 inhabitants had died by mass suicide—a claim that remains debated among historians. In modern times, the story of Masada was interpreted as a symbol of heroism that became influential in early Israeli national identity.

Excavations led by archaeologist Yigael Yadin in the 1960s uncovered remarkably preserved remains, including Herod's palaces, storerooms with food remnants, ritual baths, a synagogue, chapel, columbaria, scrolls, and pottery shards bearing names, one inscribed "ben Ya'ir," possibly linked to the final days of the defenders. The surrounding Roman siege works and bases remain visible and are among the most intact examples of Roman military engineering. Today, Masada is a UNESCO World Heritage Site and one of Israel's most popular tourist attractions, drawing around 750,000 visitors a year.