A tamga, or tamgha (from Old Turkic: 𐱃𐰢𐰍𐰀, romanized: tamğa, lit. 'stamp, seal'), was an abstract seal or brand used by Eurasian nomads and cultures influenced by them, initially as a livestock branding. The tamga was used as a livestock branding for a particular tribe, clan or family. They were common among the Eurasian nomads throughout Classical Antiquity and the Middle Ages. As clan and family identifiers, the collection and systematic comparison of tamgas is regarded to provide insights into relations between families, individuals and ethnic groups in the steppe territory.

Similar tamga-like symbols were sometimes adopted by sedentary peoples adjacent to the Pontic–Caspian steppe both in Eastern Europe and Central Asia. Branding of livestock was a common practice across most sedentary populations, as far back as the ancient Egyptians.

It has been speculated that Turkic tamgas represent one of the sources of the Old Turkic script of the 6th–10th centuries, but since the mid-20th century, this hypothesis is widely rejected as being unverifiable.

Tamgas originate in prehistoric times, but their exact usage and development cannot be continuously traced over time. There are, however, symbols represented in rock art that are referred to as tamgas or tamga-like. If they serve to record the presence of individuals at a particular place, they may be functionally equivalent to medieval tamgas.

In the later phases of the Bosporan Kingdom of the Crimea, the ruling dynasty applied personal tamgas, composed of a fragment representing the family and a fragment representing the individual king, apparently in continuation of steppe traditions and in an attempt to consolidate sedentary and nomadic factions within the kingdom.

According to Clauson (1972, p.504f.), Common Turkic tamga means "originally a `brand' or mark of ownership placed on horses, cattle, and other livestock; it became at a very early date something like a European coat of arms or crest, and as such appears at the head of several Türkü and many O[ld] Kir[giz] funary monuments".

Among modern Turkic peoples, the tamga is a design identifying property or cattle belonging to a specific Turkic clan, usually as a cattle brand or stamp. In Turkestan, it has remained what it originally was: a cattle brand and clan identifier. The Turks who remained pastoral nomad kings in eastern Anatolia and Iran, continued to use their clan tamgas and in fact, they became high-strung nationalistic imagery. The Aq Qoyunlu and Qara Qoyunlu, like many other royal dynasties in Eurasia, put their tamga on their flags and stamped their coinage with it.

When Turkish clans took over more urban or rural areas, tamgas dropped out of use as pastoral ways of life became forgotten. That is most evident in the Turkish clans that took over western and eastern Anatolia after the Battle of Manzikert. The Turks who took over western Anatolia founded the Sultanate of Rûm and became Roman-style aristocrats. Most of them adopted the then-Muslim symbol of the Seal of Solomon after the Sultanate disintegrated into a mass of feuding ghazi states (see Isfendiyarids, Karamanids). Only the Ottoman ghazi state (later to become the Ottoman Empire) kept its tamga, which was so highly stylized that the bow was stylized down eventually to a crescent moon.