Grass Wonder is an American-bred, Japanese-trained Thoroughbred racehorse and sire. In a racing career which lasted from 1997 until 2000 he won nine of his fifteen races including four Grade I races. He was the leading juvenile colt in Japan in 1997 when he was unbeaten in four races, culminating in a victory in the Asahi Hai Sansai Stakes. He missed most of his second season with injury problems but returned in autumn to win the Arima Kinen. He reached his peak as a four-year-old when he won the Takarazuka Kinen and a second Arima Kinen. He failed to win in three races in 2000 and was retired to stud. He has had some success as a breeding stallion.

The Asahi Hai Futurity Stakes (朝日杯フューチュリティステークス) is a one mile turf stakes race for thoroughbred colts two years old. It is considered the de facto year-end championship for Japanese thoroughbred racing in the two-year-olds division.