Seonjong yeonggajip (Essence of Zen Buddhism) is a book series for which King Sejo (7th King of Joseon, who reigned from 1455 to 1468) personally provided commentary on the grammatical elements of reading Chinese characters. The book series was translated into Korean by Shin Mi and others and consists of a total of four volumes. The first publication of the series was issued from Gangyoungdogam (a temporary office responsible for translating and publishing Buddhist scriptures) in 1464.

Each volume is marked with the official proofread stamp, and although four pages are missing from the last volume, the series is considered the best-preserved series of its kind. The series was published in the early years of the creation of Hangeul (the Korean alphabet) and offers invaluable information for the study of the Korean alphabet, Buddhism, and bibliography.