The majority of the scenes involving castles in the film were shot at Castle Doune in Scotland.
There were a few exceptions, notably scenes including Castle Stalker, also in Scotland.
“I fart in your general direction! Your mother was a hamster and your father smelt of elderberries!” screamed a French knight at King Arthur in the 1975 comedy film “Monty Python and the Holy Grail.” Fans of the film who remember those immortal lines and more can still visit the place where those scenes were shot, at the Doune Castle in Scotland.
https://youtu.be/QSo0duY7-9s
According to PRI report, members of Monty Python hoped to shoot the film across a variety of castles in Scotland. But due to a last-minute mix-up, they only received permission to shoot at Doune, where they ended up filming the majority of castle scenes.
This led to the crew's being rather creative with their camera angles, passing off the one castle as the scene of multiple locations. Doune was used as the location for Castle Anthrax, Camelot, and Swamp Castle in the film.
For decades afterward, the castle became the site of annual pilgrimages by Monty Python fans, and starting in 2004 the area even celebrated a Monty Python Day, where fans took tours of the castle and watched actors recreate scenes.
However, a small number of scenes were also shot at Castle Stalker, also in Scotland. In the film it was known as Castle Aaargh.
https://youtu.be/2PckeXD7Xyc
Given that majority of the castle scenes, but not all of them, were shot at Castle Doune, we rate this claim as “Mostly True.”
