Nirvikalpa samadhi, samadhi without vikalpa, mental construct, names the deepest grade of meditative absorption recognized in classical yogic and Vedantic literature, a state in which even the subtle residue of distinction between the meditator and the object of meditation, still present in savikalpa samadhi, is said to disappear entirely, leaving what practitioners and texts describe as pure, undifferentiated awareness with no remaining sense of a separate self observing anything.
In Advaita Vedanta this state is treated as the closest a temporary meditative experience can come to directly tasting the tradition's ultimate claim, that the individual self and Brahman are not two, though Advaita teachers are careful to distinguish even nirvikalpa samadhi, as an experience that begins and ends, from sahaja samadhi or jivanmukti, a permanent, effortless realization that does not depend on remaining in a special meditative state at all. Ramakrishna, the nineteenth century Bengali mystic, is among the best documented modern practitioners reported to have entered nirvikalpa samadhi repeatedly and for extended periods, and accounts of his life became an influential modern reference point for what the state was understood to involve.