Thrace (; Greek: , Thráki; Bulgarian: , Trakiya; Turkish: Trakya) is a geographical and historical region in Southeast Europe, now split among Bulgaria, Greece and Turkey, which is bounded by the Balkan Mountains to the north, the Aegean Sea to the south and the Black Sea to the east. It comprises southeastern Bulgaria (Northern Thrace), northeastern Greece (Western Thrace) and the European part of Turkey (East Thrace).
The word Thrace was established by the Greeks for referring to the Thracian tribes, from ancient Greek Thrake (), descending from Thr?ix (?). It referred originally to the Thracians, an ancient Indo-European people inhabiting Southeast Europe. The name Europe first referred to Thrace proper, prior to the term vastly extending to refer to its modern concept.  The region could have been named after the principal river there, Hebros, possibly from the Indo-European arg "white river" (the opposite of Vardar, meaning "black river"), According to an alternative theory, Hebros means "goat" in Thracian.
The historical boundaries of Thrace have varied. The ancient Greeks employed the term "Thrace" to refer to all of the territory which lay north of Thessaly inhabited by the Thracians, a region which "had no definite boundaries" and to which other regions (like Macedonia and even Scythia) were added. In one ancient Greek source, the very Earth is divided into "Asia, Libya, Europa and Thracia". As the Greeks gained knowledge of world geography, "Thrace" came to designate the area bordered by the Danube on the north, by the Euxine Sea (Black Sea) on the east, by northern Macedonia in the south and by Illyria to the west. This largely coincided with the Thracian Odrysian kingdom, whose borders varied over time. After the Macedonian conquest, this region's former border with Macedonia was shifted from the Struma River to the Mesta River. This usage lasted until the Roman conquest. Henceforth, (classical) Thrace referred only to the tract of land largely covering the same extent of space as the modern geographical region.[clarification needed] In its early period, the Roman province of Thrace was of this extent, but after the administrative reforms of the late 3rd century, Thracia's much reduced territory became the six small provinces which constituted the Diocese of Thrace. The medieval Byzantine theme of Thrace contained only what today is East Thrace.
Most of the Bulgarian and Greek population are Orthodox Christians, while most of the Turkish inhabitants of Thrace are Sunni Muslims.
Ancient Greek mythology provides the Thracians with a mythical ancestor Thrax, the son of the war-god Ares, who was said to reside in Thrace. The Thracians appear in Homer's Iliad as Trojan allies, led by Acamas and Peiros. Later in the Iliad, Rhesus, another Thracian king, makes an appearance. Cisseus, father-in-law to the Trojan elder Antenor, is also given as a Thracian king.
Homeric Thrace was vaguely defined, and stretched from the River Axios in the west to the Hellespont and Black Sea in the east. The Catalogue of Ships mentions three separate contingents from Thrace: Thracians led by Acamas and Peiros, from Aenus; Cicones led by Euphemus, from southern Thrace, near Ismaros; and from the city of Sestus, on the Thracian (northern) side of the Hellespont, which formed part of the contingent led by Asius. Ancient Thrace was home to numerous other tribes, such as the Edones, Bisaltae, Cicones, and Bistones in addition to the tribe that Homer specifically calls the "Thracians".
Thrace is mentioned in Ovid's Metamorphoses, in the episode of Philomela, Procne, and Tereus: Tereus, the King of Thrace, lusts after his sister-in-law, Philomela. He kidnaps her, holds her captive, rapes her, and cuts out her tongue. Philomela manages to get free, however. She and her sister, Procne, plot to get revenge, by killing her son Itys (by Tereus) and serving him to his father for dinner. At the end of the myth, all three turn into birds – Procne into a swallow, Philomela into a nightingale, and Tereus into a hoopoe.
The indigenous population of Thrace was a people called the Thracians, divided into numerous tribal groups. The region was controlled by the Persian Empire at its greatest extent, and Thracian soldiers were known to be used in the Persian armies. Later on, Thracian troops were known to accompany neighboring ruler Alexander the Great when he crossed the Hellespont which abuts Thrace, during the invasion of the Persian Empire itself.
The Thracians did not describe themselves by name; terms such as Thrace and Thracians are simply the names given them by the Greeks.
Divided into separate tribes, the Thracians did not form any lasting political organizations until the founding of the Odrysian state in the 4th century BC. Like Illyrians, the locally ruled Thracian tribes of the mountainous regions maintained a warrior tradition, while the tribes based in the plains were purportedly more peaceable. Recently discovered funeral mounds in Bulgaria suggest that Thracian kings did rule regions of Thrace with distinct Thracian national identity.
Sections of Thrace particularly in the south started to become hellenized before the Peloponnesian War as Athenian and Ionian colonies were set up in Thrace before the war. Spartan and other Doric colonists followed them after the war. The special interest of Athens to Thrace is underlined by the numerous finds of Athenian silverware in Thracian tombs. In 168 BC, after the Third Macedonian war and the subjugation of Macedonia to the Romans, Thrace also lost its independence and became tributary to Rome. Towards the end of the 1st century BC Thrace lost its status as a client kingdom as the Romans began to directly appoint their kings.  This situation lasted until 46 AD, when the Romans finally turned Thrace into a Roman province (Romana provincia Thracia)
During the Roman domination, within the geographical borders of ancient Thrace, there were two separate Roman provinces, namely Thrace ("provincia Thracia") and Lower Moesia ("Moesia inferior"). Later, in the times of Diocletian, the two provinces were joined and formed the so-called "Dioecesis Thracia". The establishment of Roman colonies and mostly several Greek cities, as was Nicopolis, Topeiros, Traianoupolis, Plotinoupolis and Hadrianoupolis resulted from the Roman Empire's urbanization. It is noteworthy that the Roman provincial policy in Thrace favored mainly not the Romanization but the Hellenization of the country, which had started as early as the Archaic period through the Greek colonisation and was completed by the end of Roman antiquity. As regards the competition between the Greek and Latin language, the very high rate of Greek inscriptions in Thrace extending south of Haemus mountains proves the complete language Hellenization of this region. The boundaries between the Greek and Latin speaking Thrace are placed just above the northern foothills of Haemus mountains.
During the imperial period many Thracians - particularly members of the local aristocracy of the cities - had been granted the right of the Roman citizenship (civitas Romana) with all his privileges. Epigraphic evidence show a large increase in such naturalizations in the times of Trajan and Hadrian, while in 212 AD the emperor Caracalla granted, with his well-known decree (constitutio Antoniniana), the Roman citizenship to all the free inhabitants of the Roman Empire.  During the same period (in the 1st-2nd century AD), a remarkable presence of Thracians is testified by the inscriptions outside the borders (extra fines) both in the Greek territory  and in all the Roman provinces, especially in the provinces of Eastern Roman Empire. 
By the mid 5th century, as the Western Roman Empire began to crumble, Thracia fell from the authority of Rome and into the hands of Germanic tribal rulers. With the fall of the Western Roman Empire, Thracia turned into a battleground territory for the better part of the next 1,000 years. The surviving eastern portion of the Roman Empire in the Balkans, later known as the Byzantine Empire, retained control over Thrace until the 8th century when the northern half of the entire region was incorporated into the First Bulgarian Empire and the remainder was reorganized in the Thracian theme. The Empire regained the lost regions in the late 10th century until the Bulgarians regained control of the northern half at the end of the 12th century. Throughout the 13th century and the first half of the 14th century, the region was changing in the hands of the Bulgarian and the Byzantine Empire (excluding Constantinople). In 1265 the area suffered a Mongol raid from the Golden Horde, led by Nogai Khan, and between 1305 and 1307 was raided by the Catalan company.
In 1352, the Ottoman Turks conducted their first incursion into the region subduing it completely within a matter of two decades and occupying it for five centuries. In 1821, several parts of Thrace, such as Lavara, Maroneia, Sozopolis, Aenos, Callipolis and Samothraki rebelled during the Greek War of Independence.
With the Congress of Berlin in 1878, Northern Thrace was incorporated into the semi-autonomous Ottoman province of Eastern Rumelia, which united with Bulgaria in 1885. The rest of Thrace was divided among Bulgaria, Greece and Turkey at the beginning of the 20th century, following the Balkan Wars, World War I and the Greco-Turkish War. In Summer 1934, up to 10.000 Jews were maltreated, bereaved and then forced to quit the region (see 1934 Thrace pogroms).
Today, Thracian is a geographical term used in Greece, Turkey and Bulgaria.
Two main gods of the Bessi Thracians were Dionysus (worshiped as Zagreus) and Bendis. Zagreus was worshipped by followers of Orphism (the name given to a set of religious beliefs and practices associated with literature ascribed to the mythical poet Orpheus), whose late Orphic hymns invoke his name. Actually Zagreus was a Thracian god prototype later known as Dionysus - the god of joy, wine and ecstasy in the Greek and Bacchus in the Roman mythology.
Holidays (mysteries) dedicated to Dionysus in Greece were called Dionysii; in Rome they were known as Bacchanalia and in Thrace as Rozalii. Orphic mysteries held in honor of Dionysus-Zagreus were performed only by devoted unmarried men. They were called a-bii, which means "not alive" because they did not lead an ordinary life. The mysteries were held in secret places far from the eyes of the ordinary people and were accompanied by choral songs and mimic games. The culmination of the mysteries was the symbolic death of the king-priest, identified with Zagreus who according to myth was torn apart by the Titans. Following the "death", the mother goddess was also symbolically born. The first part was carried out through a sacrifice of a bull, horse, goat or even people and the latter through a sexual orgy. Later on, Orphic mysteries became a part of the Bacchanalia.
Wine and fire were essential to the cult of Dionysus. The act of wine producing itself was recognized as a tale of the life and sorrow of the god. Picking and smashing the vines represent the way that the Titans tore Dionysus apart. That is why vinification was a mystery that was accompanied by sad songs.
Bendis was a goddess worshiped in Southwestern Thrace. She was typically presented as a hunter, wrapped with leather with boots and a fox fur hat. She holds a spear, a bow or a net and she is often accompanied by a hunting dog. In Greek mythology boots are a symbol of speed. Bendis is different from her Greek analogies in that she wears a fox hat.
Vine and Haberlea rhodopensis (Orpheus' flower) were objects of cult for the Bessi. Wine and flame were believed to cause euphoria. Svetonii Tranquil and Herodotus described rituals in which worshippers would divine by pouring wine on the altar and observing the height of the blaze. Other tribes would also burn a sacrificial animal on the altar. They believed that if the flames were vigorous, the year would be fruitful.