Panthalassa（Japanese: パンサラッサ; Chinese: 本初之海; foaled March 1, 2017) is a retired Japanese race horse whose main victories include the 2022 Dubai Turf and the 2023 Saudi Cup.

[1] The name of the horse comes from the prehistoric superocean that surrounded Pangea, derived from his sire's name, which is from a God of the seas.

Panthalassa made his debut with Ryusei Sakai　as his jockey at a mile-long maiden race held at the Hanshin Racecourse on September 21, where he came in 6th place behind Lotus Land.

His victory coincided with the Queen Elizabeth II Cup, where Akai Ito, the same horse that beat him in his second race, won.

Panthalassa attempted to widen the gap at the final stretch but was caught by Jack d'Or and finished second.

On October 26, Yoshito Yahagi announced that he had accepted the invitation to that year's Hong Kong Cup and that the horse would head to Sha Tin after the Tenno Sho.

[9] Four days after the announcement was made, the horse competed in the Autumn edition of the Tenno Sho, held at the Tokyo Racecourse.

His victory marked the first Japanese-trained horse ever to win the Saudi Cup, earning him the US$10 million, which is the highest purse of any race in the world.

However, he started from the furthest outside gate and was unable to take the lead from Remorse, resulting in the horse sinking into the pack by the fourth corner, finishing 10th.

[17] Trainer Yoshito Yahagi commented, "The horse showed no problems after the race, but we had already planned to retire him by the end of this year, so perhaps this was a good stopping point.

He was very different from Contrail (the winner of 5 GI races including the Japanese Triple Crown, also trained by Yahagi) who is the same age as him, but we never thought he'd go this far".