The RSPCA say over 500 horses in the UK have been abandoned in the past year, because their owners don't have enough money to keep them.
That figure is much higher than it's been in previous years, so the problem's getting worse.
The charity says that the cost of looking after the animals has risen dramatically in recent years.
They're encouraging people to think twice before they take the big step of buying a horse or a pony.
Hayley's been to find out more about the problem.