Fujiwara no Kamatari (藤原 鎌足, 614 – November 14, 669), also known as Nakatomi no Kamatari, was a Japanese politician and aristocrat who, together with Prince Naka no Ōe (later Emperor Tenji), carried out the Taika Reform. He was the founder of the Fujiwara clan, the most powerful aristocratic family in Japan during the Nara and Heian periods. He, along with the Mononobe clan, was a supporter of Shinto and fought the introduction of Buddhism to Japan. The Soga clan, defenders of Buddhism in the Asuka period, defeated Kamatari and the Mononobe clan, and Buddhism became the dominant religion of the Imperial Court. Kamatari was appointed Inner Minister, and, along with Prince Naka no Ōe, later Emperor Tenji (626–672), launched the Taika Reform of 645, which centralized and strengthened the central government. Just before his death, he received the surname Fujiwara and the rank Taishōkan from Emperor Tenji, thus establishing the Fujiwara clan.
Kamatari was born to the Nakatomi clan, an aristocratic kin group claiming descent from their ancestral god Ame-no-Koyane. He was the son of Nakatomi no Mikeko, and named Nakatomi no Kamatari (中臣 鎌足) at birth. His early life and exploits are described in the 8th century clan history Tōshi Kaden (藤氏家伝).
He was a friend and supporter of the Prince Naka no Ōe, later Emperor Tenji. Kamatari was the head of the Jingi no Haku, or Shinto ritualists; as such, he was one of the chief opponents of the increasing power and prevalence of Buddhism in the court, and in the nation. As a result, in 645, Prince Naka no Ōe and Kamatari made a coup d'état in the court. They slew Soga no Iruka who had a strong influence over Empress Kōgyoku; thereafter, Iruka's father, Soga no Emishi, committed suicide.
Empress Kōgyoku was forced to abdicate in favor of her younger brother, who became Emperor Kōtoku; Kōtoku then appointed Kamatari naidaijin (Inner Minister).
Kamatari was a leader in the development of what became known as the Taika Reforms, a major set of reforms based on Chinese models and aimed at strengthening Imperial power.