Magatama (勾玉; less frequently 曲玉) are curved, comma-shaped beads that appeared in prehistoric Japan from the Final Jōmon period through the Kofun period, approximately 1000 BCE to the 6th century CE. The beads, also described as jewels, were made of stone and earthen materials in the early period, but by the end of the Kofun period were made almost exclusively of jade. Magatama originally served as decorative jewelry, but by the end of the Kofun period functioned as ceremonial and religious objects.

Magatama first appeared in Japan in the Final Jōmon period (1000–300 BCE), and in this period were made from relatively simple, naturally occurring materials, including clay, talc, slate, quartz, gneiss, jadeite, nephrite, and serpentinite. Magatama from the Jōmon period were irregularly shaped, lacked continuity in form from region to region, and have been called "Stone Age magatama" for this reason. Magatama are thought to be an imitation of the teeth of large animals, pierced with a hole, which are found in earlier Jōmon remains. These resemble magatama, but more recent scholarship indicates that these early Jōmon may have simply had a decorative function, and have no relationship to magatama. Magatama in the Jōmon period appear to have moved from the purely decorative to having a status and ceremonial function by the end of the period. A "middle Jōmon exchange network" may have existed, whereby magatama were produced in regions where materials for their manufacture were readily plentiful. Jade and talc examples produced in bead-making villages located in present-day Itoigawa, Niigata have been found at a large number of sites along the northern coast, in the central mountains, and in Kantō region.

Examples of magatama from the Jōmon period have been discovered in large numbers at the Kamegaoka site in Tsugaru, Aomori Prefecture. The Kamegaoka remains are among the largest known Jōmon settlement in Japan, and the magatama, among other decorative objects found, may be an indicator of the high social status of the settlement.

Other sites associated with the Kamegaoka settlement have yielded magatama, including the Ōboriya shell mound, in the northwest corner of Ōfunato Bay, which yielded a huge number of beads, as well as the Korekawa site, near Hachinohe, Aomori Prefecture. Remains from the Korekawa site can be seen at the Korekawa Archaeological Museum in Hachinohe. Stone and clay magatama and magatama-like beads have also been discovered at the Amataki site, Ninohe, Iwate Prefecture, Osagata site, Ibaraki Prefecture, and the Kou site, Fujiidera, Osaka Prefecture. Numerous magatama at the Ōishi site, Bungo-ōno, Ōita Prefecture, Kyushu show signs of being used for ceremonial, rather than decorative, purposes.

The Sannai-Maruyama Site, excavated 1992 in Aomori, Aomori Prefecture, yielded three large jade beads measuring 5.5 by 6.5 centimetres (2.2 in × 2.6 in).

Magatama in the Yayoi period (300 BCE – 300 CE) are notably different from Jōmon-period magatama. The jewels moved from a primitive, non-standard form towards more polished and uniform form in this period. The technology to cut large gemstones and polish jewels notably advanced in the Yayoi period. Refined materials such as jadeite, serpentinite, and glass replaced the less sophisticated materials of the Jōmon period. Yayoi period magatama are noted for their reverse C-shaped form, which by the end of the period had become an almost squared shape. From the Yayoi period onwards, magatama uniformly feature a bored hole that allowed the jewels to be held on a string.

The Yayoi period is marked by specific geographic centers specializing in magatama and the widespread trade of magatama. The period is marked by the formation of power centers that came to be individual states. The development of weapons increased in this period to protect increasingly developed rice fields and fishing rights. Trade greatly increased in this period, as did the specialization of production of certain items, including magatama. Magatama producing areas exchanged their product with other products, specifically rice, leading to the widespread distribution of magatama across Japan. Magatama were commonly used to create necklaces and bracelets worn on the wrists or ankles. The necklace was typically constructed of jadeite magatama separated by cylindrical bored-holed pieces of jasper. Small beads of dark-blue glass are also not uncommon on the necklace. The bracelet typically also used shells from the coastal areas of Shikoku and the Inland Sea, wood, and bronze. In this period the use of the mirror, sword, and jewels as status symbols for village, and later regional leaders of all kinds, emerged in the Yayoi period, and point to the origin of the mirror, sword, and magatama as the Imperial Regalia of Japan.

The Records of the Three Kingdoms, the earliest historical document with a reference to Japan, describes the Wa people, an ancient country of Yamatai, and its queen, Himiko. The Record indicates that when Himiko died, her relative Iyo, a girl of 13, was made queen and sent a delegation of twenty officials under Yazuku, an imperial general, to offer tribute to the Northern Wei court. "The delegation visited the capital and offered to the court five thousand white gems and two pieces of carved jade, as well as twenty pieces of brocade with variegated designs." The carved jade in the Record likely describes a tribute of two jade magatama.