Near the beginning of the film, Laurence Harvey's character is shot with an arrow full in the chest by Rex Harrison's character, knocking him off his horse. Yet Harvey gets up and spends the rest of the movie with no sign of a wound, nor any mention of one.
Saladin is depicted as ignorant of the existence of ice. In fact, ice was found in the mountains of the Middle East, and was used to cool drinks. Saladin famously offered King Guy of Jerusalem a cup of iced water after the battle of Hattin, in an incident which led to the killing of Reynaud de Châtillon, Lord of Oultrejourdain.
Much of the heraldry depicted is incorrect. The arms of Montferrat are argent, a chief gules (white or silver, with a red band at the top), not the fanciful design with fleurs-de-lys depicted in the film.
Conrad, Marquis of Montferrat, is described as a "wise Venetian" in the script, ignoring the fact that his title indicated where he is from. Montferrat (Monferrato) is in Piedmont, in NW Italy; Venice is in the NE.
During the joust scene, in the first pass the combattants correctly gallop with the central barrier on their left (shielded) side. In the second pass, they wrongly gallop with the barrier on their unshielded side.
During the battle scene clouds of arrows are shot at the attacking cavalry; and while
many men are hit, not a single horse is hit, wounded or killed.
During the horse chase scenes to rescue the Lady Edith, when close-ups are shown of either King Richard or Sir Giles, the "horses" are clearly plastic dummies.
Many of Lady Edith's figure fitting gowns have visible zippers up the back.
The camels in the movie are Bactrian (Asian two-humps), whereas camels in the Middle East are dromedary (one-hump).