The rider was taking the horse for a stroll in woodland near Wick Hill Lane, Finchampstead, when the horse had attempted to cross a ditch, but instead fell in.
The rider escaped unharmed, but the large black horse - said to be around 23 years old and around 5”6 - rolled on to its back and could not free itself.
Three fire engines, one from Bracknell, one from Whitely and they Large Animal Rescue unit from Caversham attended the scene, at around 10.30am.
Watch manager Micheal Fulwell, from Bracknell, said: “We had to walk down a footpath and bridle path so there was no cranes!
“The vet gave the horse something to calm him down, and it was a case of digging the banks and trying to free him, the sides were very muddy.
“We spent about 45 minutes there before we finally got the horse out to everyone’s relief, it stood up took a few steps and seemed alright.”