Agnes Tachyon (Japanese : アグネスタキオン, April 13, 1998 - June 22, 2009) was an undefeated Japanese Thoroughbred racehorse and a Leading sire in Japan. He was by Sunday Silence, his dam, Agnes Flora (by ) won the Oka Sho (Japanese 1000 Guineas) and his granddam won the Yushun Himba (Japanese Oaks). Agnes Flora also produced the Tokyo Yushun (Japanese Derby) winner Agnes Flight.