Śubhakarasiṃha (637?-735), known as Shànwúwèi (善無畏) in Mandarin, Zemmui in Japanese, and Seonmuoe in Korean, was an Indian Buddhist monk and Esoteric Buddhist master who showed up in China in AD 716 and became involved in translating several tantric Buddhist texts from Sanskrit into Chinese, most notably the Mahāvairocana Sūtra.
Four years later another master, Vajrabodhi (670-741), and his pupil Amoghavajra (705-775), would arrive and proceeded to translate additional tantric scriptures. Along with these other masters, Śubhakarasiṃha was responsible for bringing Esoteric Buddhism into vogue in Tang China.
According to Chinese sources, Śubhakarasiṃha was born to royalty as the prince of a minor kingdom in the northern part of what would become the Indian state of Orissa. Because of his abilities and popularity, his father bypassed his older brothers and named him crown prince. However, when he ascended to the throne at the tender age of 13, his jealous brothers raised a rebellion against him. Although Śubhakarasiṃha defeated his brothers, he was so dismayed by warfare that he turned over the kingdom to his eldest brother anyway and abdicated to become a Buddhist monk.
Travelling widely in his youth, he finally ended up at the university at Nālandā under the tutlege of a Buddhist master named Dharmagupta. After several years of training, including wandering around central India debating non-Buddhists into submission, Śubhakarasiṃha was eventually told by Dharmagupta that he had a karmic connection with China and must go to China to spread Buddhist teachings there.
Śubhakarasiṃha took his time getting to China. Travelling north, he stopped for several years in the kingdom of Oḍḍiyāna in what is now northern Pakistan, passing the time as an instructor to the king, before finally passing into China via Tibet. Śubhakarasiṃha's fame had preceded him, and he was supposedly met at the border of China by a welcoming party sent by Tang emperor Ruizong. It took several more years for Śubhakarasiṃha to work his way north through China, and he did not finally arrive in the Tang capital at Chang'an (present-day Xi'an) until 716.
Chinese sources assert that Śubhakarasiṃha was born in 637, which would have made him 79 years old when he reached Chang'an, and 98 years old when he died in 735. However, there was a tradition of Buddhist monks claiming to be much older than they appeared in order to buttress their claims to supernatural powers (Śubhakarasiṃha's teacher Dharmagupta, for example, was supposedly more than 800 years old when he met Śubhakarasiṃha, even though he only looked about 40). Moreover, researchers have tentatively identified Śubhakarasiṃha with the teenage usurper of a small kingdom in northern Orissa named Mādhavarāja III, who ruled much later, in the late 600s, so Śubhakarasiṃha might actually have only been around age 40 when he arrived in Chang'an and around 60 when he died.
Having finally arrived in Chang'an, Śubhakarasiṃha took up residence in the Ximing temple and received an imperial command to begin translating the hundreds of sutras he had brought with him into Chinese. However, shortly after beginning his work, the Xuanzong emperor ordered all of his sutras confiscated for reasons that are uncertain, but perhaps due to pressure from Daoist monks who resented the growing power of Buddhism.
Left with nothing to work on, Śubhakarasiṃha travelled with his disciple, the Chinese monk Yixing, to the Huayan temple in Datong, where he received several Sanskrit texts, including the Mahāvairocana Sūtra. Thereafter, Śubhakarasiṃha settled in Luoyang and began his translation work, ably assisted by Yixing. In 725, Śubhakarasiṃha and Yixing completed their translation of the Mahāvairocana Sūtra into Chinese, along with a commentary, and proceeded to translate several other texts as well.
Finally in 732, Śubhakarasiṃha declared his translation work finished and petitioned the Emperor for permission to return home to his native India. However, Śubhakarasiṃha was considered too valuable to lose, and permission was denied. Three years later Śubhakarasiṃha passed away and was given a state funeral with a variety of high honors. His passing was said to have been personally mourned by the Xuanzong emperor himself.
After Śubhakarasiṃha's passing, his disciple Yixing inherited his teachings and ultimately passed them on to the Korean monk Huiguo, who later passed them on to the legendary Japanese monk Kūkai when Kūkai visited China from 804-806. Śubhakarasiṃha's teachings thus went on to become the core teachings of the Shingon sect of Japanese Buddhism and the Mahāvairocana Sūtra that Śubhakarasiṃha translated remains the most important text in Shingon to this day.