The Shurangama or Śūraṅgama mantra is a dhāraṇī or long mantra of Buddhist practice in China, Japan and Korea. Although relatively unknown in modern Tibet, there are several Śūraṅgama Mantra texts in the Tibetan Buddhist canon. It is associated with Chinese Esoteric Buddhism and Shingon Buddhism.
The Mantra was, according to the opening chapter of the Śūraṅgama Sūtra, historically transmitted by Gautama Buddha to Manjushri to protect Ananda before he had become an arhat. It was again spoken by the Buddha before an assembly of monastic and lay adherents. 
Like the popular six-syllable mantra "om mani padme hum" and the Nīlakaṇṭha Dhāraṇī, the Śūraṅgama mantra is synonymous with practices of Avalokiteśvara, an important bodhisattva in both East Asian Buddhism and Tibetan Buddhism. The Śūraṅgama Mantra also extensively references Buddhist deities such as the bodhisattvas Manjushri, Mahākāla, Sitatapatra Vajrapani and the Five Tathagatas, especially Bhaisajyaguru. It is often used for protection or purification for meditators and is considered to be part of Shingon Buddhism in Japan.
Within the Śūraṅgama Sūtra , the Sanskrit incantation (variously referred to as dhāraṇī or mantra) contained therein, is known as the Sitātapatroṣṇīṣa dhāraṇī, The "Śūraṅgama mantra" (Chinese: 楞嚴咒) is well-known and popularly chanted in East Asian Buddhism, where it is very much related to the practice of the "White Parasol Dhāraṇī" (Chinese: 大白傘蓋陀羅尼). In Tibetan Buddhism, it is the "White Umbrella" (Wylie: gdugs dkar)..
The currently popular version of the Śūraṅgama Sūtra and Śūraṅgama mantra were translated and transliterated from Sanskrit to Chinese characters during the Tang dynasty by the monk Paramiti from North India and reviewed by Meghashikara from Oddiyana after Empress Regnant Wu Zetian retired in the year 705.