was a samurai member of the Minamoto clan, who fought in the Hōgen and Heiji Rebellions and in the Genpei War. He was the adopted son of Minamoto no Tameyoshi since age thirteen. Sasaki fought under Minamoto no Yoshitomo in the Hōgen Rebellion (1156), aiding in the siege of the Shirakawa palace. Three years later, he fought for the Minamoto again in the Heiji Rebellion, incurring the ire of the rival Taira clan.