The Ippon Shinno (the first-ranked imperial prince) was the imperial prince who was granted Ippon, the highest rank (status) under the ritsuryo system (a system of centralized government based on the ritsuryo code).
一品親王（いっぽんしんのう）とは、律令制において皇親に対して与えられた最も高い品位(身位)である一品を与えられた親王のこと。