The Siege of Amida was a siege of the Roman city Amida in 359 of the Sassanids under Shah Shapur II.

When the Persian forces approached Amida, the Sassanids were provoked into attacking the city. This came about when the son of Grumbates, king of the Xionites, a tribe allied with the Persians , while inspecting the defences of Amida, was shot and killed with an arrow shot by the city garrison. Ammianus described how the Grumbates, outraged at his son's death, demanded revenge from the Romans: he compares the death to that of Patroclus at Troy. The Sassanids began the attack with siege towers and attempted to take the city hastily, but were largely unsuccessful. Unable to gain a quick victory, Shapur had to commit to capturing Amida in order to appease his ally.

The siege took 73 days. Shapur attempted to capture the city several times but every time it ended with disaster. Many times siege towers were set on fire by the Romans. During the siege, plague broke out in Amida but ended after ten days by a light rain. A day before capture of the city, Ammianus Marcellinus escaped to Melitene, and thence returned to Antioch.

After capturing the city, Shapur II advanced further and took Singara and some other fortresses in the following years. In 363, Emperor Julian, at the head of a strong army, advanced to Ctesiphon, but was killed in a battle. His successor Jovian signed a treaty of peace, by which the districts on the Tigris and Nisibis (totalling five Roman provinces) were ceded to the Persians, and the Romans promised to interfere no more in Armenia.