Acerra (Italian: [aˈtʃɛrra]) is a town and comune of Campania, southern Italy, in the Metropolitan City of Naples, about 15 kilometres (9 miles) northeast of the capital in Naples. It is part of the Agro Acerrano plain.

Acerra is one of the most ancient cities of the region, likely founded by the Osci with the name of Akeru (Latin: Acerrae, Ancient Greek: Ἀχέρραι). It first appears in history as an independent city during the great war of the Campanians and Latins against Rome. Shortly after the conclusion, in 332 BC, the Acerrani, in common with several other Campanian cities, obtained the Roman "civitas", without the right of suffrage. The period at which the latter privilege was granted upon them is not mentioned, however, it is certain that they ultimately obtained full rights over the Roman citizens.

In the Second Punic War, the city was faithful to the Roman alliance, on which account it was besieged by Hannibal in 216 BC, following which the city was quickly abandoned by the inhabitants in despair, leading the city to be plundered and burnt. After the expulsion of Hannibal from Campania, the Acerrani, with the consent of the Roman senate, returned to and rebuilt their city in 210 BC.

Acerra served as a Roman base during the Social War in 90 BC. During the war, it was besieged by the Samnite General, Gaius Papius Mutilus, but offered so vigorous a resistance that he was unable to reduce it. Virgil praises the fertility of its territory, but the town itself had suffered so much from the frequent inundations of the river Clanius, on which it was situated, that it was in his time almost deserted. It subsequently received a colony under Augustus, and Strabo speaks of it in conjunction with Nola and Nuceria, apparently as a place of some consequence. It does not seem, however, to have retained its colonial rank, but is mentioned by Pliny as an ordinary municipal town.

In 826 the Lombards built a castle here, which was later demolished by Bono of Naples. In 881 it was sacked by the Saracens. Later it became a Norman possession, the seat of a county. As part of the Kingdom of Naples, it was a domain of the Aquino, the Origlia, the Orsini del Balzo and, from 1496 until 1812, the Cardenas. From 1927 it was part of the province of Terra di Lavoro.

On 1 October 1943, several units of the Hermann Göring Division massacred nearly 90 civilians, including 7 children and 14 women in one of the bloodiest massacres in Campania; a memorial was erected in honor and on behalf of the victims.

From the 1990s to the 2000s, a waste management crisis broke out in the city as a result of illegal dumping by the Pellini brothers, Camorra members. The majority of the waste was dumped in the region between Acerra, Nola, and Marigliano, referred to as the "Triangle of Death". A 2004 study by Alfredo Mazza published in The Lancet Oncology revealed that deaths by cancer in the area are much higher than the European average. In 2009, the Acerra incineration facility was completed at a cost of more than €350 million. The incinerator burns 600,000 tons of waste per year in order to produce refuse-derived fuel. The energy produced from the facility is enough to power 200,000 households per year.

After this incinerator was built in 2009, there was yet again another trash epidemic in 2011. There were more than 2,000 tons of uncollected trash, with over 170 troops deployed into the area. Since 2008, the 2011 crisis is the second time troops have been deployed in order to deal with the issue. Prime Minister Silvio Berlusconi ordered the troops to "return Naples to being a civilized city."