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 Royal Ski) won the Oka Sho (Japanese 1000 Guineas) and his granddam Agnes Lady won the Yushun Himba (Japanese Oaks).

Agnes Tachyon was undefeated in his four race starts, including Satsuki Sho (Japanese 2000 Guineas), before a bowed tendon ended his racing career.

Agnes Tachyon's descendants include:[2] c = colt, f = filly Agnes Tachyon was the Leading sire in Japan in 2008 and died in June 2009, due to heart failure.

[4] An anthropomorphized version of the horse appears in Uma Musume Pretty Derby, with a movie featuring the character titled Uma Musume Pretty Derby: Shinjidai no Tobira released in Japan on May 24, 2024.