Bodhisattva (Skt.; Pāli, bodhisatta, ‘Enlightenment-Being’; Chin., P'u-sa; Jap., Bosatsu; Korean, Posal; Tib., byang.chub sems.dpa, ‘Hero of the Thought of Enlightenment’). In Theravāda Buddhism a title exclusively identifying historical Buddhas (i.e. Śākyamuni) in their previous lives, before their Buddhahood was attained; and in Mahāyāna Buddhism to describe any being who, out of compassion, has taken the bodhisattva vow to become a Buddha for the sake of all sentient beings. Strictly, an ordinary person who has ‘engendered bodhicitta’ (generated a desire for enlightenment in order to save all beings from suffering) and taken the bodhisattva vow is a bodhisattva, but there are also ‘celestial bodhisattvas’, such as Mañjuśrī and Avalokiteśvara, who are almost Buddhas in their attainments.

A bodhisattva's progress is determined by his practice of the six (sometimes given as ten) perfections (pāramitās) which are: generosity and morality; patience and energy; meditation and wisdom.

This contrast between the bodhisattva and the arhat or pratyekabuddha ideals is the principal distinction between the Mahāyāna and Theravāda schools, since the overwhelming message of the Mahāyāna is that the nirvāna with which the arhats and pratyekabuddhas content themselves is not the highest goal. Some bodhisattvas, such as Avalokiteśvara, who in some Tibetan schools is considered to have already attained Buddhahood, even enter the hell-realms in order to alleviate pain there. The Mahāyāna notion of the bodhisattva as a being who views his own comfort (and sometimes his vows) as concerns subordinate to the needs of others, thus increased the social dimension of Buddhism and emphasized the value of lay life alongside monkhood. In Vimalakīrtinirdeśa-sūtra (c.2nd-3rd cents. CE), for example, it is the lay bodhisattva Vimalakīrti who is the hero, and Mañjuśrī is the only other bodhisattva deemed wise enough to converse with him.