The Thracians were an ancient collection of tribes inhabiting the eastern and southeastern Balkans (mainly modern Bulgaria, northeast Greece, European Turkey, and parts of Romania and North Macedonia). They were Indo-European speaking and first mentioned by Greek sources in the 1st millennium BC. Renowned as fierce warriors and skilled horsemen, Thracians lived in both tribal chiefdoms and larger kingdoms (such as the Odrysian kingdom). Culturally, they left rich tombs (e.g., the Thracian tombs of Kazanlak and Sveshtari with exquisite gold treasures) and were known for their passionate music and worship of deities like Dionysus (the Greek god of wine, who likely has Thracian origins). Thracian warriors often served as mercenaries (including in Alexander the Great’s army). The Thracians never unified into a single empire and were eventually conquered: parts of Thrace fell under Persian rule briefly, but ultimately the Romans annexed Thrace by the 1st century AD. Over time, Thracians became Hellenized or Latinized within the Roman Empire, and by the Middle Agestheir distinct identity had faded (with the exception of possibly contributing to the ethnogenesis of the Bulgarians and other Balkan peoples).

Genetically, Thracians would have been similar to other Iron Age Europeans in the Balkans. They had a mix of ancestry from Neolithic farmers (who came from Anatolia millennia prior) and Indo-European steppe pastoralists (who arrived during the Bronze Age). Ancient DNA from remains in what was ancient Thrace shows continuity with modern Southeast Europeans, implying that Thracian bloodlines were absorbed into later Balkan populations. For example, genetic analyses indicate that people in Bulgaria and Romania today still carry significant components of ancestry that match Iron Age Balkan samples. Thracians likely carried Y-DNA haplogroups such as J2, E-V13, R1a, and I2, all of which are found among present-day Balkan men and are consistent with a mix of early European farmer and steppe influences. The arrival of Slavs and Bulgars in the 6th–7th centuries AD added new genetic layers, but the substrate in the region (partly Thracian) remained important. Thus, while the Thracians asa culture disappeared, their genes live on amalgamated with those of later peoples, contributing to the modern genetic mosaic of the Balkans.