Artificial cranial deformation or modification, head flattening, or head binding is a form of body alteration in which the skull of a human being is deformed intentionally. It is done by distorting the normal growth of a child's skull by applying pressure. Flat shapes, elongated ones (produced by binding between two pieces of wood), rounded ones (binding in cloth), and conical ones are among those chosen or valued in various cultures.

Typically, the alteration is carried out on an infant, when the skull is most pliable. In a typical case, head binding begins approximately a month after birth and continues for about six months.

Intentional cranial deformation predates written history; it was practiced commonly in a number of cultures that are widely separated geographically and chronologically, and still occurs today in a few areas, including Vanuatu.

The earliest suggested examples were once thought to include Neanderthals and the Proto-Neolithic Homo sapiens component (9th millennium BCE) from Shanidar Cave in Iraq. The view that the Neanderthal skull was artificially deformed was common for a period. However, later research by Chech, Grove, Thorne, and Trinkaus, based on new cranial reconstructions in 1999, questioned the earlier findings and concluded: "we no longer consider that artificial cranial deformation can be inferred for the specimen". It is thought elongated skulls found among Neolithic peoples in Southwest Asia were the result of artificial cranial deformation.

The earliest written record of cranial deformation comes from Hippocrates in about 400 BCE. He described a group known as the Macrocephali or Long-heads, who were named for their practice of cranial modification.

In the Old World, the practice of cranial deformation was brought to Bactria and Sogdiana by the Yuezhi, a tribe that created the Kushan Empire. Men with such skulls are depicted in various surviving sculptures and friezes of that time, such as the Kushan prince of Khalchayan.

Alchon kings are generally recognized by their elongated skulls, a result of artificial skull deformation. Archaeologist Cameron Petrie wrote that "The depictions of elongated heads suggest that the Alchon kings engaged in skull modification, which was also practised by the Hun groups that appeared in Europe." The elongated skulls appear clearly in most portraits of rulers in the coinage of the Alchon Huns, and most visibly on the coinage of Khingila. These elongated skulls, which they obviously displayed with pride, distinguished them from other peoples, such as their predecessors the Kidarites. On their coins, the spectacular skulls came to replace the Sasanian crowns which had been current in the region's coinage. This practice is also known among other peoples of the steppes, particularly the Huns, and as far as Europe, where it was introduced by the Huns themselves.

In the Pontic steppe and the rest of Europe the Huns, including the Proto-Bulgarians, are also known to have practiced similar cranial deformation, as were the Alans.