Rebirth in Buddhism refers to the teaching that the actions of a sentient being lead to a new existence after death, in an endless cycle called saṃsāra. This cycle is considered to be dukkha, unsatisfactory and painful. The cycle stops only if moksha (liberation) is achieved by insight and the extinguishing of craving. Rebirth is one of the foundational doctrines of Buddhism, along with karma, Nirvana and liberation. Rebirth was however less relevant among early Buddhist teachings, which also mentioned the beliefs in an afterlife, ancestor worship, and related rites. The concept varies among different Buddhist traditions.

The rebirth doctrine, sometimes referred to as reincarnation or transmigration, asserts that rebirth takes place in one of the six realms of samsara, the realms of gods, demi-gods, humans, the animal realm, the ghost realm and hell realms. Rebirth, as stated by various Buddhist traditions, is determined by karma, with good realms favored by kushala karma (good or skillful karma), while a rebirth in evil realms is a consequence of akushala karma (bad karma). While nirvana is the ultimate goal of Buddhist teaching, much of traditional Buddhist practice has been centered on gaining merit and merit transfer, whereby one gains rebirth in the good realms and avoids rebirth in the evil realms.

The rebirth doctrine has been a subject of scholarly studies within Buddhism since ancient times, particularly in reconciling the rebirth doctrine with its anti-essentialist anatman (not-self) doctrine. The various Buddhist traditions throughout history have disagreed on what it is in a person that is reborn, as well as how quickly the rebirth occurs after each death.

Some Buddhist traditions assert that vijñana (consciousness), though constantly changing, exists as a continuum or stream (santana) and is what undergoes rebirth. Some traditions like Theravada assert that rebirth occurs immediately and that no "thing" (not even consciousness) moves across lives to be reborn (though there is a causal link, like when a seal is imprinted on wax). Other Buddhist traditions such as Tibetan Buddhism posit an interim existence (bardo) between death and rebirth, which may last as long as 49 days. This belief drives Tibetan funerary rituals. A now defunct Buddhist tradition called Pudgalavada asserted there was an inexpressible personal entity (pudgala) which migrates from one life to another.