According to multiple sources, the rarest horse breeds in the world are:

1. American Cream Draft
2. Akhal-Teke Horse
3. Dales Pony
4. Suffolk Punch Horse
5. Cleveland Bay Horse
6. Sorraia
7. Nokota Horse
8. Galiceño
9. Choctaw Indian Pony
10. Hackney Horse
11. Eriskay Pony
12. Camarillo White Horse

The rarity of a breed is determined by factors such as population size, distribution, and degree of inbreeding within the breed. Some of these breeds are considered endangered species and could soon be wiped out within a generation despite conservation efforts and legal protections.