The Art of the Japanese Language (Portuguese: Arte da Lingoa de Iapam and in modern Portuguese: Arte da Língua do Japão; Japanese: 日本大文典, Nihon Daibunten) is an early 17th-century Portuguese grammar of the Japanese language. It was compiled by João Rodrigues, a Portuguese Jesuit missionary. It is the oldest fully extant Japanese grammar and is a valuable reference for the late middle period of the Japanese language.