Crews from Newport, Shanklin and Ventnor are in attendance at the scene off Whitwell Road, alongside the Animal Rescue Unit from Newport and the Land Rover 4×4 from Ryde.
Firefighters, who were alerted to the plight of the large animal at 08:10, are using their specialist equipment in a bid to free the horse.
A vet from Vectis Equine Vets has been called.
UPDATE @ 10:00 – The horse has been successfully freed from the ditch, albeit a little sore.
The Isle of Wight Fire and Rescue Service has now stood down from the incident.