name by which North China was known in medieval Europe. The word is derived from Khitay (or Khitan), the name of a seminomadic people who left southeastern Mongolia in the 10th century CE to conquer part of Manchuria and northern China, which they held for about 200 years. By the time of Genghis Khan (died 1227), the Mongols had begun referring to North China as Kitai and South China as Mangi. Kitai is still the Russian word for China.

Either Muslim merchants or two Franciscan friars who visited the ancient Mongol capital of Karakorum in 1246 and 1254 are thought to have introduced the name Cathay to Europe. But Marco Polo (Polo, Marco) (1254–1324), who journeyed to China almost 50 years later, was the one who really put the image of Cathay before the European public. His descriptions of a Cathay that possessed a far more sophisticated culture and technology than the contemporary West were circulated throughout medieval Europe. Following the collapse of Mongol power in the 14th century, European contact with China was lost, but stories of the country persisted. Christopher Columbus (Columbus, Christopher) and John Cabot (Cabot, John) thought they were heading toward Cathay in their voyages to the New World. In fact Columbus, who had a copy of Marco Polo's book with him, believed he had reached Mangi, which he described as contiguous to Cathay. It was not ascertained that China and Cathay were the same place until the Spanish Augustinian friar Marin de Rade, in 1575, and the Jesuit Matteo Ricci (Ricci, Matteo), in 1607, recorded the fact when they proved that China could be reached by following Marco Polo's land route across Central Asia.