Worin cheongangjigok (Songs of the Moon's Reflection on a Thousand Rivers) is a Buddhist hymn book written by Queen Soheon (1395-1446), queen consort of King Sejong (1418-1450), the fourth monarch of the Joseon Dynasty (1392-1910), whose greatest achievements include the invention of hangeul, the Korean alphabet, now called Hunminjeongeum (The Proper Sounds for the Instruction of the People).
It is one of the first to be published using movable metal types following the promulgation of the Hunminjeongeum, and, accordingly, is widely regarded as a very important material for study of the Korean linguistics and book printing history in the early stage after creation of the Hangeul (Korean alphabet). Although two thirds of the original volumes of the book have been lost, it has nonetheless been widely recommended for listing as a National Treasure in recognition its outstanding value regarding the origins of the Korean writing system and the development of book printing in Korea.