In Buddhist philosophy and soteriology, Buddha-nature (Chinese: fóxìng 佛性, Japanese: busshō 佛性, Vietnamese: Phật tính, Sanskrit: buddhatā, buddha-svabhāva or tathāgatagarbha तथागतगर्भ) is the innate potential for all sentient beings to become a Buddha or the fact that all sentient beings already have a pure Buddha-essence within themselves. "Buddha-nature" is the common English translation for several related Mahāyāna Buddhist terms, most notably tathāgatagarbha (तथागतगर्भ) and buddhadhātu, but also sugatagarbha, and buddhagarbha. Tathāgatagarbha can mean "the womb" or "embryo" (garbha) of the "thus-gone one" (tathāgata), and can also mean "containing a tathāgata". Buddhadhātu can mean "buddha-element", "buddha-realm", or "buddha-substrate".

Buddha-nature has a wide range of (sometimes conflicting) meanings in Indian Buddhism and later in East Asian and Tibetan Buddhist literature. Broadly speaking, it refers to the belief that the luminous mind, "the natural and true state of the mind", which is pure (visuddhi) mind undefiled by afflictions, is inherently present in every sentient being, and is eternal and unchanging. It will shine forth when it is cleansed of the defilements, that is, when the nature of mind is recognized for what it is.

The Mahāyāna Mahāparinirvāṇa Sūtra (2nd century CE), which was very influential in the Chinese reception of these teachings, linked the concept of tathāgatagārbha with the buddhadhātu. The term buddhadhātu originally referred to the relics of Gautama Buddha. In the Mahāyāna Mahāparinirvāṇa Sūtra, it came to be used in place of the concept of tathāgatagārbha, reshaping the worship of physical relics of the historical Buddha into worship of the inner Buddha as a principle of salvation.

The primordial or undefiled mind, the tathāgatagārbha, is also often equated with the Buddhist philosophical concept of emptiness (śūnyatā, a Mādhyamaka concept); with the storehouse-consciousness (ālāyavijñāna, a Yogācāra concept); and with the interpenetration of all dharmas (in East Asian traditions like Huayan). The belief in Buddha-nature is central to East Asian Buddhism, which relies on key Buddha-nature sources like the Mahāyāna Mahāparinirvāṇa Sūtra. In Tibetan Buddhism, the concept of Buddha-nature is equally important and often studied through the key Indian treatise on Buddha-nature, the Ratnagotravibhāga (3rd–5th century CE).

The term tathāgatagarbha may mean "embryonic tathāgata", "womb of the tathāgata", or "containing a tathagata". Various meanings may all be brought into mind when the term tathagatagarbha is being used.

The Sanskrit term tathāgatagarbha is a compound of two terms, tathāgata and garbha:

The Chinese translated the term tathāgatagarbha as rúláizàng (如来藏), or "Tathāgata's (rúlái) storehouse" (zàng). According to Brown, "storehouse" may indicate both "that which enfolds or contains something", or "that which is itself enfolded, hidden or contained by another." The Tibetan translation is de bzhin gshegs pa'i snying po, which cannot be translated as "womb" (mngal or lhums), but as "embryonic essence", "kernel" or "heart". The term "heart" was also used by Mongolian translators.

The Tibetan scholar Go Lotsawa outlined four meanings of the term Tathāgatagarbha as used by Indian Buddhist scholars generally: (1) As an emptiness that is a nonimplicative negation, (2) the luminous nature of the mind, (3) alaya-vijñana (store-consciousness), (4) all bodhisattvas and sentient beings.