A tzompantli (Nahuatl pronunciation: [t͡somˈpant͡ɬi]) or skull rack was a type of wooden rack or palisade documented in several Mesoamerican civilizations, which was used for the public display of human skulls, typically those of war captives or other sacrificial victims. It is a scaffold-like construction of poles on which heads and skulls were placed after holes had been made in them. Many have been documented throughout Mesoamerica, and range from the Epiclassic (c. 600–900 CE) through early Post-Classic (c. 900–1250 CE). In 2015 archeologists announced the discovery of the Huey Tzompantli, with more than 650 skulls, in the archeological zone of the Templo Mayor in Mexico City.

The name comes from the Classical Nahuatl language of the Aztecs but is also commonly applied to similar structures depicted in other civilizations. Its precise etymology is uncertain although its general interpretation is 'skull rack', 'wall of skulls', or 'skull banner'. It is most likely a compound of the Nahuatl words tzontecomatl ('skull'; from tzontli or tzom- 'hair', 'scalp' and tecomatl ('gourd' or 'container'), and pamitl ('banner'). That derivation has been ascribed to explain the depictions in several codices that associate these with banners; however, Nahuatl linguist Frances Karttunen has proposed that pantli means merely 'row' or 'wall'.

It was most commonly erected as a linearly-arranged series of vertical posts connected by a series of horizontal crossbeams. The skulls were pierced or threaded laterally along these horizontal stakes. An alternate arrangement, more common in the Maya regions, was for the skulls to be impaled on top of one another along the vertical posts.

Tzompantli is known chiefly for their depiction in Late Postclassic (13th to 16th centuries) and post-Conquest (mid-16th to 17th centuries) codices, contemporary accounts of the conquistadores, and several other inscriptions. However, a tzompantli-like structure, thought to be the first instance of such structures, has been excavated from the Proto-Classic Zapotec civilization at the La Coyotera, Oaxaca site, dating from around the 2nd century BCE to the 3rd century CE. The Zapotecs called this structure a yàgabetoo, and it displayed 61 skulls.

Tzompantli are also noted in other Mesoamerican pre-Columbian cultures, such as the Toltec and Mixtec.

At the Toltec capital of Tula the first indications in Central Mexico of a real fascination with skulls and skeletons. Tula flourished from the ninth until the thirteenth century. The site includes the decimated remains of a tzompantli. The tzompantli at Tula displayed multiple rows of stone carved skulls adorning the sides of a broad platform upon which the actual skulls of sacrificial victims were exhibited. The tzompantli appeared during the final phases of civilization at Tula, which was destroyed around 1200.

Other examples are indicated from Maya civilization sites such as Uxmal and other Puuc region sites of the Yucatán, dating from around the late 9th-century decline of the Maya Classical Era. A particularly fine and intact inscription example survives at the extensive Chichen Itza site.

Human sacrifice on a large scale was introduced to the Maya by the Toltecs from the appearances of the tzompantli in the Chichen Itza ball courts. Six ball court reliefs at Chichen Itza depict the decapitation of a ball player; it seems that the losers would be beheaded and would have their skulls placed on the tzompantli.