Ātman (/ˈɑːtmən/), attā or attan in Buddhism is the concept of self, and is found in Buddhist literature's discussion of the concept of non-self (Anatta). Most Buddhist traditions and texts reject the premise of a permanent, unchanging atman (self, soul).

Cognates (Sanskrit: आत्मन्) ātman, Pāli atta, Old English æthm, and German Atem derive from the Indo-European root *ēt-men (breath). The word means "essence, breath, soul."

Ātman and atta refer to a person's "true self", a person's permanent self, absolute within, the "thinker of thoughts, feeler of sensations" separate from and beyond the changing phenomenal world. The term Ātman is synonymous with Tuma, Atuma and Attan in early Buddhist literature, state Rhys David and William Stede, all in the sense of "self, soul". The Atman and Atta are related, in Buddhist canons, to terms such as Niratta (Nir+attan, soulless) and Attaniya (belonging to the soul, having a soul, of the nature of soul).

"Atman" in early Buddhism appears as "all dhammas are not-Self (an-atta)", where atta (atman) refers to a metaphysical Self, states Peter Harvey, that is a "permanent, substantial, autonomous self or I". This concept refers to the pre-Buddhist Upanishads of Hinduism, where a distinction is made between the personal self, jivatman (impermanent body, personality) and the Real Self, Atman. The early Buddhist literature explores the validity of the Upanishadic concepts of self and Self, then asserts that every living being has an impermanent self but there is no real Higher Self. The Nikaya texts of Buddhism deny that there is anything called Ātman that is the substantial absolute or essence of a living being, an idea that distinguishes Buddhism from the Brahmanical (proto-Hindu) traditions.

The Buddha argued that no permanent, unchanging "Self" can be found. In Buddha's view, states Wayman, "eso me atta, or this is my Self, is to be in the grip of wrong view". All conditioned phenomena are subject to change, and therefore can't be taken to be an unchanging "Self". Instead, the Buddha explains the perceived continuity of the human personality by describing it as composed of five skandhas, without a permanent entity (Self, soul).

Of the early Indian Buddhist schools, only the Pudgalavada-school diverged from this basic teaching. The Pudgalavādins asserted that, while there is no ātman, there is a pudgala or "person", which is neither the same as nor different from the skandhas.

Buddha-nature is a central notion of east-Asian (Chinese) Mahayana thought. It refers to several related terms, most notably Tathāgatagarbha and Buddha-dhātu. Tathāgatagarbha means "the womb of the thus-gone" (cf. enlightened one), while Buddha-dhātu literally means "Buddha-realm" or "Buddha-substrate". Several key texts refer to the tathāgatagarbha or Buddha-dhātu as "atman", Self or essence, though those texts also contain warnings against a literal interpretation. Several scholars have noted similarities between tathāgatagarbha texts and the substantial monism found in the atman/Brahman tradition.

The Tathagatagarbha doctrine, at its earliest, probably appeared about the later part of the 3rd century CE, and is verifiable in Chinese translations of 1st millennium CE.