Acireale (Italian: [ˌatʃireˈaːle]; Sicilian: Jaciriali, locally shortened to Jaci or Aci) is a coastal city and municipality in the north-east of the Metropolitan City of Catania in the autonomous region of Sicily in Italy, at the foot of Mount Etna, on the coast facing the Ionian Sea. With a population of 50,579, it is the second-largest municipality in the metropolitan city.

It is home to numerous churches, including the Neo-Gothic St. Pietro's Basilica, St. Sebastiano's Basilica in the Sicilian Baroque style, and the 17th century Acireale Cathedral, and a seminary, for the training of priests. Acireale is also noted for its art and paintings: the oldest academy in Sicily, the Accademia di scienze, lettere e belle arti degli Zelanti e dei Dafnici, is located here.

According to tradition, the city's origins trace back to Xiphonia, a mysterious Greek city whose location is unknown. In Roman times, there existed another Greek town, Akis, which was involved in the Punic Wars. In Ovid's Metamorphoses, there is a great love between Ā́cis, the spirit of the Ā́cis River, and Galatea the sea-nymph. According to mythology, the tears of Galatea after the death of Ā́cis gave birth to the Ā́cis River, Fiume di Jaci, flowing past Acireale (the ancient Akis or Acium). The Romans called the town Acium, and it was on the main road from Catana to Tauromenium. The Romans used the thermal springs located here.

In the Middle Ages, the town expanded around the castle (now part of Aci Castello), known as Jachium under the Byzantines, as Al-Yāj (الياج) under the Arabs, and, later, as Aquilia. The potent 1169 Sicily earthquake scattered the population of the city farther into the mainland, divided between the numerous boroughs of Aci. Another town, Aquilia Nova ("New Aquilia"), was founded in the late 14th century further north, creating the nucleus of what is now Acireale. The only extant architectural remnant of this medieval town is Gothic-Lombard-style portal of the church of Sant'Antonio di Padova.

In the 16th century, Emperor Charles V freed the city from feudal ties, creating it as a Crown commune. In the late 16th century, the town had between 6,000 and 7,000 inhabitants. The most ancient document mentioning the Carnival of Acireale dates to 1594. The town expanded its role as a trade center (it was granted the right to hold a Free Market or Fiera Franca) and received numerous new edifices.

Acireale was nearly destroyed by the massive 1693 Sicily earthquake, which substantially halted its economic growth, and required near-complete reconstruction of all the buildings. During the Expedition of the Thousand in 1861, led by Garibaldi and which liberated Sicily from the rule of the Bourbon Kingdom of Napoli, Acireale was the first town to rebel against the Neapolitan rule. In 1941, the town was bombed by the Allies, resulting in many civilian casualties.^{[citation needed]}

As of 2025, the municipality has a population of 50,579, of whom 48.7% are male and 51.3% are female. Minors make up 15.2% of the population, and pensioners make up 23.7%, compared to the Italian average of 14.9% minors and 24.7% pensioners.

The city had grown in the second half of the 19th century as a "City of Studies" because there was a heritage of several boarding schools and institutions of higher education that today can be considered lost in the absence of a university campus. In Acireale there are several Secondary schools, public and private, divided between high schools, technical and professional institutes, which are also largely frequented by students from neighboring municipalities.