She was born on a farm in America to a couple who specialise in breeding miniature horses.
Standing just 17 inches tall, she is never going to be a champion show-jumper.
In fact, the tiny mare is so small she would struggle to leap over a bucket.
But such things are of little concern for feisty Thumbelina who has just been officially recognised as the world's smallest horse.
The five-year-old received the title from the Guinness Book of Records after her astonished owners realised she was never going to grow any bigger
I think that thumbelina is so beautiful! She must be very spoiled...
