Fujiwara no Mototsune , also known as Horikawa Daijin (堀川大臣), was a Japanese statesman, courtier and aristocrat of the early Heian period. He was the first kampaku, a regent of an adult emperor, in Japanese history.

In Japan, Sesshō (摂政) was a title given to a regent who was named to act on behalf of either a child emperor before his coming of age, or an empress regnant. The Kampaku (関白) was theoretically a sort of chief advisor for the Emperor, but was in practice the title of both first secretary and regent who assisted an adult Emperor. The duties of the Sesshō and Kampaku were to convey to the Emperor the policies formulated by the Sadaijin and other senior officials of the Daijō-kan , and to convey the Emperor's decisions to them. As regents of the Emperor, the Sesshō and Kampaku sometimes made decisions on behalf of the Emperor, but their positions were not defined by law and they had no specific political authority. The two titles were collectively known as sekkan (摂関), and the families that exclusively held the titles were called sekkan-ke.