Crystal skulls are human skull hardstone carvings made of clear, milky white or other types of quartz (also called "rock crystal"), claimed to be pre-Columbian Mesoamerican artifacts by their alleged finders; however, these claims have been refuted for all of the specimens made available for scientific studies. The results of these studies demonstrated that those examined were manufactured in the mid-19th century or later, almost certainly in Europe, during a time when interest in ancient culture abounded. The skulls appear to have been crafted in Germany, quite likely at workshops in the town of Idar-Oberstein, which was renowned for crafting objects made from imported Brazilian quartz in the late 19th century.

Despite some claims presented in an assortment of popularizing literature, legends of crystal skulls with mystical powers do not figure in genuine Mesoamerican or other Native American mythologies and spiritual accounts. The skulls are often claimed to exhibit paranormal phenomena by some members of the New Age movement, and have often been portrayed as such in fiction. Crystal skulls have been a popular subject appearing in numerous science fiction television series, novels, films, and video games.

Trade in fake pre-Columbian artifacts developed during the late 19th century to the extent that in 1886, Smithsonian archaeologist William Henry Holmes wrote an article called "The Trade in Spurious Mexican Antiquities" for Science. Although museums had acquired skulls earlier, it was Eugène Boban, an antiquities dealer who opened his shop in Paris in 1870, who is most associated with 19th-century museum collections of crystal skulls. Most of Boban's collection, including three crystal skulls, was sold to the ethnographer Alphonse Pinart, who donated the collection to the Trocadéro Museum, which later became the Musée de l'Homme.

Many crystal skulls are claimed to be pre-Columbian, usually attributed to the Aztec or Maya civilizations. Mesoamerican art has numerous representations of skulls, but none of the skulls in museum collections come from documented excavations. Research carried out on several crystal skulls at the British Museum in 1967, 1996 and 2004 shows that the indented lines marking the teeth (for these skulls had no separate jawbone, unlike the Mitchell-Hedges skull) were carved using jeweler's equipment (rotary tools) developed in the 19th century, making a pre-Columbian origin untenable.

The type of crystal used for these skulls was identified by examination of chlorite inclusions. It is only found in Madagascar and Brazil, and thus unobtainable or unknown within pre-Columbian Mesoamerica. The study concluded that the skulls were crafted in the 19th century in Germany, quite likely at workshops in the town of Idar-Oberstein, which was renowned for crafting objects made from imported Brazilian quartz in the late 19th century.

It has been established that the crystal skulls in the British Museum and Paris's Musée de l'Homme were originally sold by the French antiquities dealer Eugène Boban, who was operating in Mexico City between 1860 and 1880. The British Museum crystal skull transited through New York's Tiffany & Co., while the Musée de l'Homme's crystal skull was donated by Alphonse Pinart, an ethnographer who had bought it from Boban.

In 1992, the Smithsonian Institution investigated a crystal skull provided by an anonymous source; the source claimed to have purchased it in Mexico City in 1960, and that it was of Aztec origin. The investigation concluded that this skull also was made recently. According to the Smithsonian, Boban acquired his crystal skulls from sources in Germany, aligning with conclusions made by the British Museum.

The Journal of Archaeological Science published a detailed study by the British Museum and the Smithsonian in May 2008. Using electron microscopy and X-ray crystallography, a team of British and American researchers found that the British Museum skull was worked with a harsh abrasive substance such as corundum or diamond, and shaped using a rotary disc tool made from some suitable metal. The Smithsonian specimen had been worked with a different abrasive, namely silicon carbide (carborundum), a silicon-carbon compound which is a synthetic substance manufactured using modern industrial techniques. Since the synthesis of carborundum dates only to the 1890s and its wider availability to the 20th century, the researchers concluded "[t]he suggestion is that it was made in the 1950s or later".