Thomas Arnold, 41, was flying his drone over 11th-century Berkeley Castle in Gloucestershire.
He mysteriously lost contact with the machine as it flew close to the medieval castle’s battlements.
When he watched the footage back at home, he was shocked to see a bizarre apparition moving across the courtyard.
He said: “When I saw it I said ‘oh my god, what’s that’.
“When I saw it I said ‘oh my god, what’s that’”
“I started zooming and rewinding and there was definitely something there.”
Thomas, from Dursley, Gloucestershire, believes he has captured the ghost of a knight on horseback riding across the deserted castle
He went on: “The drone lost contact with the control, which was with me.
“I pressed the ‘return to home’ key, but it wasn’t until I got home that we noticed what I would describe as an apparition going through the courtyard.”
Thomas had only bought the drone two days earlier when he took it for a flight over the castle on Thursday.
He said that there was no doubt in his mind that the white shape was a ghost.
At first, he thought it might be smoke, but checking the footage he saw that none of the castle’s chimneys were producing smoke and the wind was blowing in the opposite direction.
Berkeley Castle has a gruesome history of its own.
Originally built in the 11th century, the Grade I listed building was the site of a grisly murder in 1327.
King Edward II, King of England, is believed by historians to have been murdered at the castle after being imprisoned there and forced to give up his crown.
Thomas says that he has always believed in ghosts.
“When I was seven or eight me and my grandfather stopped to talk to a neighbour, Mrs Bramble, and I remember sitting on a bench talking to her.
“We got home and my grandma asked what had kept us, and when we told her we had been talking to Mrs Bramble she told us she’d died the night before.”
The horse is not the only ghostly sighting in the south of England recently.