| Iago | 1843 | Pot 8 o's系 |
| Icecapade | 1969 | Nearctic系 |
| Imbros | 1950 | Sickle系 |
| Impeccable | 1944 | Hyperion系 |
| Imperial Ballet | 1989 | Sadler's Wells系 |
| In Reality | 1964 | Intent系 |
| Intent | 1948 | Man o'War系 |
| Internationally | 1956 | Intent系 |
| In the Purple | 1966 | Owen Tudor系 |
| In the Wings | 1986 | Sadler's Wells系 |
| Intikhab | 1994 | Roberto系 |
| Ion | 1835 | Herod系 |
| Irish Castle | 1967 | Bold Ruler系 |
| Irish Lancer | 1957 | Royal Charger系 |
| Irish River | 1976 | Never Bend系 |
| I Say | 1962 | Nearco系 |
| Isinglass | 1890 | Pot 8 o's系 |
| Is It True | 1986 | Bold Ruler系 |
| Isonomy | 1875 | Pot 8 o's系 |
| Ithuriel | 1841 | Pot 8 o's系 |