Olopen, Olopan, or Olopuen (probably a Chinese form of the Syriac Rabban, i.e. monk) (fl. 7th century) was the first Christian missionary in China (setting aside vague stories of St Thomas, St Bartholomew, &c.), and founder of the Nestorian Church in the Far East.

According to the Nestorian Stele, our sole authority, Olopen came to China from Ta Tsin (the Roman empire) in the ninth year of the emperor Tai-Tsung (635 AD), bringing sacred books and images. He was received with favor; his teaching was examined and approved; his Scriptures were translated for the imperial library; and in 638 an imperial edict declared Christianity a tolerated religion. Tai-Tsung's successor, Kao-Tsung (650-683), was still more friendly, and Olopen now became a guardian of the empire and lord of the great law. After this followed (c. 683-744) a time of disfavour and oppression for Chinese Christians, followed by a revival dating from the arrival of a fresh missionary, Kiho, from the Roman empire.