Varna (Bulgarian: Варна, pronounced [ˈvarnɐ]) is the third-largest city in Bulgaria and the largest city and seaside resort on the Bulgarian Black Sea Coast and in the Northern Bulgaria region. Situated strategically in the Gulf of Varna, the city has been a major economic, social, and cultural centre for almost three millennia. Historically known as Odessos (Ancient Greek: Ὀδησσός), Varna developed from a Thracian seaside settlement into a major seaport on the Black Sea.

Varna is a significant hub for business, transportation, education, tourism, entertainment, and healthcare. The city is referred to as the maritime capital of Bulgaria and is home to the headquarters of the Bulgarian Navy and merchant marine. In 2008, Varna was designated as the seat of the Black Sea Euroregion by the Council of Europe. In 2014, Varna was awarded the title of European Youth Capital 2017.

The oldest gold treasure in the world, belonging to the Varna culture, was discovered in the Varna Necropolis and dated to 4600–4200 BC. Since the discovery of the Varna Necropolis in 1974, 294 burial sites have been excavated, with over 3000 golden items inside.

Theophanes the Confessor first mentions the name Varna, as the city came to be known, within the context of the Slavic conquest of the Balkans in the 6th to 7th centuries. The name could be of Varangian origin, as Varangians had been crossing the Black Sea for many years, reaching Constantinople in the early Middle Ages. In Swedish, värn means 'shield, defense' – hence Varna could mean 'defended, fortified place'. Vikings invaded the settlement during the Middle Ages. The name may be older than that; perhaps it derives from the Proto-Indo-European root *u̯er- 'to flow, wet, water, river' (cf. Varuna), or from the Proto-Slavic root varn 'black', or from Iranian bar or var 'camp, fortress' (see also Etymological list of provinces of Bulgaria).

According to Theophanes, in 680, Asparukh, the founder of the First Bulgarian Empire, routed an army of Constantine IV near the Danube River delta. Pursuing those forces, he reached "the so-called Varna near Odyssos [sic] and the midlands thereof" (τὴν λεγομένην Βάρναν, πλησίον Ὀδυσσοῦ). Perhaps the new name applied initially to an adjacent river or lake, a Roman military camp, or an inland area, and only later to the city itself.

By the late 10th century, the name Varna was established so firmly that when Byzantines wrested back control of the area from the Bulgarians around 975, they kept it rather than restoring the ancient name Odessos.

Prehistoric settlements are best known for the Chalcolithic necropolis (mid-5th millennium BC radiocarbon dating), a key archaeological site in world prehistory, the eponymous Varna culture, and internationally regarded as the world's oldest large find of gold artifacts, which existed within modern city limits. In the wider region of the Varna lakes (before the 1900s, freshwater) and the adjacent karst springs and caves, over 30 prehistoric settlements have been unearthed, with the earliest artefacts dating back to the Middle Paleolithic or 100,000 years ago.

Since the late Bronze Age (13th–12th c. BC), the area around Odessos had been populated with Thracians. During the 8th–9th c. BC local Thracians had active commercial and cultural contacts with people from Anatolia, Thessaly, the Caucasus, and the Mediterranean Sea. These links were reflected in some local productions, for example, forms of bronze fibula of the age, either imported or locally made. There is no doubt that interactions occurred mostly by sea, and the bay of Odessos is one of the places where the exchanges took place. Some scholars consider that during the 1st millennium BC, the region was also settled by the half-mythical Cimmerians. An example of their, probably accidental, presence is the tumulus dated 8th–7th c. BC found near Belogradets, Varna Province.