Yi Kyubo (1168–1241) was a Korean scholar, literary critic, poet and writer of the Koryo period. Approximately 1,500-2,000 of his poems and numerous prose works survive. Korea didn't develop the hangul writing system until the 15th century; these earlier works were written using hanmun characters. The 13th century Collected Works of Minister Yi of Korea by Yi Kyubo is one of the earliest texts of a Korean writer commissioned by an official patron.