Aléria (French pronunciation: [aleʁja]; Ancient Greek: Ἀλαλίη/Ἀλλαλία, Alalíē/Allalía; Latin and Italian: Aleria; Corsican: U Cateraghju) is a commune in the Haute-Corse department of France on the island of Corsica, former bishopric and present Latin Catholic titular see. It includes the easternmost point in Metropolitan France.

Aléria shares the canton of Moïta-Verde with 13 other communes: Moïta, Ampriani, Campi, Canale-di-Verde, Chiatra, Linguizzetta, Matra, Pianello, Pietra-di-Verde, Tallone, Tox, Zalana and Zuani.

Aléria is 70 km (43 mi) to the south of Bastia on Route N198, in the centre of the Plaine Orientale, also called the Plaine d'Aléria, the east-central coastal plain of the island facing Italy. It includes a number of villages and monuments. Most of the rest of the island is precipitously mountainous.

The eastern coastline is punctuated by a number of lakes connecting (but not always) to the Tyrrhenian Sea, the remnant of an ancient system of lagoons behind barrier beaches. The Corsicans refer to them under the name of Étang, "pool", although most are larger by far than an English pool. Marshland is also extensive on the coast requiring that cities be built inland from it. Malaria has historically been a problem near the marshlands and swamps of eastern Corsica. The fine barrier beaches are a recreational attraction.

The Tavignano River (Tavignanu) enters the commune to the northwest and exits into the Tyrrhenian Sea. Its lands include a delta, marshes to the south and the unconnected Étang de Diane to the north. To the west, the étang de Terre Rosse is a lake and reservoir used to irrigate the plain.

Corsica had an indigenous population in the Neolithic and the Bronze Age but the east coast was subject to colonization by Mediterranean maritime powers: Greeks, Etruscans, Carthaginians, Romans. They typically built on an étang, which they used as a harbor. Alalíē (Ionic dialect) was placed between the southern end of the 3.5 km (2.2 mi) long Ētang de Diane and the Tavignano River (the classical Rhotanos), slightly inland, but controlling the entire district including the mouth of the river. The site is partly occupied today by the village of Cateraggio (Corsican: U Cateraghju) at the crossroads of national routes N200 and N198. N200 follows the Vallé du Tavignano into the interior mountains of Corte.

When the Etruscans took the district, after its abandonment by the Greeks, they settled further south along N198 in the vicinity of the village of Aléria, today primarily an archaeological site across the river from Cateraggio, where visitors and academics are quartered. Still south of there was the Etruscan necropolis, in today's Casabianda. Aléria takes its name from the Roman town placed there after the defeat of the Etruscans.

The entire district, however, is wider still, following the Corsican custom of including some mountains and some beaches in every district. It incorporates the agricultural lands of Teppe Rosse (to the west), the entire Étang de Diane and the Plage de Padulone 3 km (2 mi) east of Cateraggio, a former barrier beach. Since 1975 a series of laws have created the Casabianda-Aléria Nature Preserve, 1,748 ha (4,320 acres) between the mouth of the Tavignanu and the Étang d'Urbinu, which is 5 km (3 mi) to the south.