Alodia, also known as Alwa (Greek: Αρουα, Aroua; Arabic: علوة, ʿAlwa), was a medieval kingdom in what is now central Sudan. Its capital was the city of Soba, located near modern-day Khartoum at the confluence of the Blue and White Nile rivers.

Founded sometime after the ancient Kingdom of Kush fell, around 350 AD, Alodia is first mentioned in historical records in 569. It was the last of the three Nubian kingdoms to convert to Christianity in 580, following Nobadia and Makuria. It possibly reached its peak during the 9th–12th centuries when records show that it exceeded its northern neighbor, Makuria, with which it maintained close dynastic ties, in size, military power and economic prosperity. Alodia was a large, multicultural state administered by a powerful king and provincial governors appointed by him. The capital Soba, described as a town of "extensive dwellings and churches full of gold and gardens", prospered as a trading hub. Goods arrived from Makuria, the Middle East, western Africa, India and even China. Literacy in both Nubian and Greek flourished.

From the 12th, and especially the 13th century, Alodia was declining, possibly because of invasions from the south, droughts and a shift of trade routes. In the 14th century, the country might have been ravaged by the plague, while Arab tribes began to migrate into the Upper Nile valley. By around 1500 Soba had fallen to either Arabs or the Funj. This likely marked the end of Alodia, although some Sudanese oral traditions claimed that it survived in the form of the Kingdom of Fazughli within the Ethiopian–Sudanese borderlands. After the destruction of Soba, the Funj established the Sultanate of Sennar, ushering in a period of Islamization and Arabization.

Alodia is by far the least studied of the three medieval Nubian kingdoms, hence evidence is very slim. Most of what is known about it comes from a handful of medieval Arabic historians. The most important of these are the Islamic geographers al-Yaqubi (9th century), Ibn Hawqal and al-Aswani (10th century), who both visited the country, and the Copt Abu al-Makarim (12th century). The events around the Christianization of the kingdom in the 6th century were described by the contemporary bishop John of Ephesus; various post-medieval Sudanese sources address its fall. Al-Aswani noted that he interacted with a Nubian historian who was "well-acquainted with the country of Alwa", but no medieval Nubian historiographical work has yet been discovered.

While many Alodian sites are known, only the capital Soba has been extensively excavated. Parts of this site were unearthed in the early 1950s, further excavations taking place in the 1980s and 1990s. A new multidisciplinary research project was scheduled to start in late 2019. Soba is approximately 2.75 km² (1.06 sq mi) in size and is covered with numerous mounds of brick rubble previously belonging to monumental structures. Discoveries made so far include several churches, a palace, cemeteries and numerous small finds.

Alodia was located in Nubia, a region which, in the Middle Ages, extended from Aswan in southern Egypt to an undetermined point south of the confluence of the White and Blue Nile rivers. The heartland of the kingdom was the Gezira, a fertile plain bounded by the White Nile in the west and the Blue Nile in the east. In contrast to the White Nile Valley, the Blue Nile Valley is rich in known Alodian archaeological sites, among them Soba. In the mid-19th century the right shore of the Blue Nile between Soba and the Rahad was reportedly still associated with the name of the kingdom. The extent of the Alodian influence to the south is unclear, although it is likely that it bordered the Ethiopian highlands. The southernmost known Alodian sites are in the proximity of Sennar.

To the west of the White Nile, Ibn Hawqal differentiated between Al-Jeblien, which was controlled by Makuria and probably corresponded with northern Kordofan, and the Alodian-controlled Al-Ahdin, which has been identified with the Nuba Mountains, and perhaps extended as far south as Jebel al Liri, near the modern border to South Sudan. Nubian connections with Darfur have been suggested, but evidence is lacking.

The northern region of Alodia probably extended from the confluence of the two Niles downstream to Abu Hamad near Mograt Island. Abu Hamad likely constituted the northernmost outpost of the Alodian province known as al-Abwab ("the gates"), although some scholars also suggest a more southerly location, nearer the Atbara River. No evidence for a major Alodian settlement has been discovered north of the confluence of the two Niles, although several forts have been recorded there.