Mahasthamaprapta, literally "arrival of a great power," (sk. Mahāsthāmaprāpta, ch: Dàshìzhì 大勢至; or dàshìzhì púsà 大勢至菩薩, jp: Seishi 勢至), is a great bodhisattva of the Western Paradise of Bliss (sk. Sukhāvatī. ch. Xīfāng jílè shìjiè 西方極樂世界).
He helps Amitābha Buddha welcome all those who have fulfilled the conditions to go to this wonderful paradise admired and praised by the Buddhas of all directions.
The Pure Land school venerates him along with Amitābha and the great bodhisattva Avalokiteśvara as one of the Three Saints of the West (ch. Xīfāng sānshèng 西方三聖). He is presented as the right-hand acolyte of Amitābha and represents the power of wisdom, while Avalokiteśvara is the left-hand acolyte and represents great compassion.
Having successfully arrived at the tenth bodhisattva land by focusing his mind on Amitābha Buddha and reciting his name, he is considered the first patriarch of the Pure Land school. Like Avalokiteśvara, he is often represented in Chinese Buddhism in female form.
His association with Amitābha and Avalokiteśvara is based on the following texts:
Canon of the Pure Land School: The Great Sūtra of Infinite Life, (sk. Mahāyāna Amitāyus sūtra, ch. Dàchéng wúliàngshòu jīng 《大乘無量壽經》)， Sūtra of the Contemplations of Infinite Life, (sk. Vipaśyana Amitāyus sūtra, ch. Guān wúliàngshòu jīng 《觀無量壽經》).
Shurangama Sutra, (ch. Léngyán jīng 《楞嚴經》), in this sutra, this great bodhisattva relates that he attained enlightenment through constant recitation of the name of Amitābha Buddha or the formula Nāmo Amitābhāya by focusing his mind on this Buddha.
Sūtra of Great Compassion in which the future Amitābha is a dharma-protecting king whose four sons are Avalokiteśvara, Mahāsthāmaprāpta, Mañjuśrī and Samantabhadra. When he attained the state of Buddha, his two eldest sons became his acolytes.
Mahāsthāmaprāpta is also one of the Thirteen Buddhas of the Japanese Shingon school, where he appears in the Mantra Matrix World Mandala: Om sam jam jam sah svâhâ (Skt.). The founder of the jōdo shū Buddhist school, Honen Shonin, is sometimes considered his incarnation.
Moreover, the Lotus Sutra counts him among those who assembled on Vulture Peak to hear Shākyamuni preach. The Gautama Buddha dedicates chapter XX to him, which illustrates the extent of compassion.
The Commentary on the Sūtra of the Lotus written by Guàndǐng 灌頂(561-632), a patriarch of the Tiantai stream, compares Avalokiteśvara to the Sun and Mahāsthāmaprāpta to the Moon.