Musō Jikiden Eishin-ryū (無双直伝英信流 or 無雙直傳英信流) is a Japanese sword art school and one of the most widely practiced schools of iai in the world. Often referred to simply as "Eishin-ryū," it claims an unbroken lineage dating back from the sixteenth century to the early 20th century. 17th undisputed headmaster, Oe Masaji, awarded at least 16 licenses of full transmission, resulting in the school fracturing into multiple legitimate branches.