Saghang Sechen Hong-tayiji 薩囊徹辰鴻台吉 (Mongolian Saγang Sečen Qung Tayiǰi; b. 1604, fl. through the 1660s, possibly to 1672) was a taišī (high-rank Mongol noble) of the Ordos 鄂爾多斯 Mongols of the Right-Wing Yeke-juu qošun (in modern Inner Mongolia, around the great loop of the Yellow River). He was the eleventh-generation descendant of Khutughtu Sechen Hong-tayiji 庫圖克徹辰鴻台吉 of the Ordos princely line and ultimately of Khabutu Sasen, taišī under Lighdan Khutughtu Qan 林丹庫圖克圖汗, the last Mongol great khan (defeated by the Manchus in 1634). He lived through the Manchu conquest of the Mongol khanates and the consolidation of Qīng overlordship over the Mongols. His one major surviving work, the Erdeni-yin tobchi 蒙古源流 (Mongolian; “Precious Summary”), translated into Chinese by Qīng imperial commission as the Qīndìng Měnggǔ yuánliú 欽定蒙古源流 KR2e0022, is the most important indigenous Mongolian historiographical source for the late-Yuán-into-Manchu period and has been the principal Mongolian historical source for European Mongolian studies since Isaac Schmidt’s 1829 German translation. Saghang Sechen completed the work in 1662 by his postface, drawing on at least seven earlier Mongol and Tibetan sources including the Hóng cè 紅冊 and a Sharba Khutughtu compilation. The catalog meta gives his name with the conventional Manchu / Qīng prefix 蒙古 (“Mongol”) attached, and his designation as a Qīng-period author reflects the dating of the Chinese translation rather than of the Mongol original. Other names: in Mongolian sources also known as Saγang Secen Qung Tayiǰi or simply Saγang Secen.