The siege of Syracuse from 877 to 878 led to the fall of the city of Syracuse, the Roman capital of Sicily, to the Aghlabids. The siege lasted from August 877 to 21 May 878 when the city, effectively left without assistance by the central Byzantine government, was sacked by the Aghlabid forces.

Following their first landing in Sicily in the late 820s, the Aghlabids had tried several times, without success, to capture Syracuse. They were able to gradually take over the western half of the island, however, and, in 875, a new and energetic governor, Ja'far ibn Muhammad, was appointed, determined to capture the city. Ja'far began the siege in August 877 but soon left it in charge of his son Abu Ishaq, while he retired to Palermo. The Arabs were well-supplied with siege weapons, while the inhabitants of Syracuse were left largely unsupported by the Byzantine fleet, which was busy with transporting marble for a new church in Constantinople and was then delayed by adverse weather. Consequently, the besieged populace faced great hardships and famine as described in detail by the eyewitness account of Theodosios the Monk. Finally, the Aghlabids managed to effect a breach in the seaward walls and on 21 May 878 managed to break through it into the city. The defenders and much of the populace were massacred, while others, including Theodosios, were taken prisoner. The Byzantine patrikios, who commanded the defense, surrendered with a few of his men, but they were executed after a week, while a handful of soldiers escaped and brought the news east to the fleet that had belatedly set sail to aid the city. The Muslims were unable to capitalize upon this success due to internal rivalries, which even led to a full-scale civil war. Small-scale warfare with the Byzantines continued without any side gaining a decisive advantage until the arrival of the deposed Aghlabid emir Ibrahim II, who in 902 rallied the Sicilian Muslims and captured Taormina, effectively completing the Muslim conquest of Sicily, although a few fortresses remained in Byzantine hands until 965.

Syracuse ( SIRR-ə-kewss, -⁠kewz; Italian: Siracusa [siraˈkuːza] (listen); Sicilian: Sarausa [saɾaˈuːsa]) is a historic city on the Italian island of Sicily, the capital of the Italian province of Syracuse. The city is notable for its rich Greek and Roman history, culture, amphitheatres, architecture, and as the birthplace of the pre-eminent mathematician and engineer Archimedes. This 2,700-year-old city played a key role in ancient times, when it was one of the major powers of the Mediterranean world. Syracuse is located in the southeast corner of the island of Sicily, next to the Gulf of Syracuse beside the Ionian Sea. It is situated in a drastic rise of land with 2,000 metres (6,600 ft) depths being close to the city offshore although the city itself is generally not so hilly in comparison.

The city was founded by Ancient Greek Corinthians and Teneans and became a very powerful city-state. Syracuse was allied with Sparta and Corinth and exerted influence over the entirety of Magna Graecia, of which it was the most important city. Described by Cicero as "the greatest Greek city and the most beautiful of them all", it equaled Athens in size during the fifth century BC. It later became part of the Roman Republic and the Byzantine Empire. Under Emperor Constans II, it served as the capital of the Byzantine Empire (663–669). Palermo later overtook it in importance, as the capital of the Kingdom of Sicily. Eventually the kingdom would be united with the Kingdom of Naples to form the Two Sicilies until the Italian unification of 1860.

In the modern day, the city is listed by UNESCO as a World Heritage Site along with the Necropolis of Pantalica. In the central area, the city itself has a population of around 125,000 people. Syracuse is mentioned in the Bible in the Acts of the Apostles book at 28:12 as Paul stayed there. The patron saint of the city is Saint Lucy; she was born in Syracuse and her feast day, Saint Lucy's Day, is celebrated on 13 December.