The Questing Beast, or the Beast Glatisant (Old French: beste glatisant, Modern French: bête glatissante), is a cross-animal monster appearing in many medieval texts of the Arthurian legend and modern works inspired by them. In the French prose cycles, and consequently in the quasi-canon of Le Morte d'Arthur, the hunt for the Beast is the subject of quests futilely undertaken by King Pellinore and his family and finally achieved by Sir Palamedes and his companions.

Its name comes from the great noise that it emits from its belly (such motif seems to have originated in a symbolic dream scene in the Gesta Regum Anglorum). Glatisant is related to the French word glapissant, 'yelping' or 'barking', especially of small dogs or foxes. Arthurian scholars tend to interpret the beast as a reflection of the medieval mythological view on giraffes, whose generic name of Camelopardalis originated from their description of being half-camel and half-leopard. According to an Arthuriana article, the beast comes from a mistranslation of the Arabic word zaraffa, leading to the description of the beast to be described as zurafa, that is docile or graceful, which is shown in the French text mentioning douce.

A Questing Beast-style, chimera-like creature first appears in the Arthurian legend in the prologue to the Vulgate Estoire del Saint Grail (History of the Holy Grail), where it is an unnamed and friendly animal that accompanies and guides the initial-narrator character in the 8th century into finding the book containing the main story:

As soon as it saw me, it got up, began to look at me, and I at it. But the longer I looked at it, the less I knew what kind of animal it was. I would have you know that it was variegated in every way: it had the head and neck of a sheep, and these were as white as new snow; and it had the feet, legs, and thighs of a dog, and all this was as black as coal; and it had the breast and body and rump of a fox and the tail of a lion. Thus it resembled various animals. After I had looked at it for a long time, and it at me, I raised my hand and signaled that it should go before me.

Within the main story, another character describes a strange and deadly monster:

We took leave of him, and when we came to Orberica, we heard a great hue and cry about a wild beast that was in the country and that the people had begun to hunt. This beast was so bizarre that no matter how long any man looked at it he could not say what it was, but it was so redoubtable and cruel that it was ravaging the entire region. It was destroying the green wheat, killing men and horses, tearing down houses, taking small children from the cradle, and crushing good pregnant women when it found them alone. [...] Nor should any man who was not armed have attacked the beast, for on its forehead it had three horns so sharp and keen that no armor, no matter how well struck, could resist them. Thus my brother pursued it before all the others, and it had already killed three horses from beneath him, as it darted back and forth in flight.

The actual Questing Beast story, originally from Post-Vulgate Suite du Merlin (Merlin Continuation), has the creature appear to the young King Arthur after he has had an affair with his half-sister Morgause and begotten Mordred (they did not know that they were related when the incestuous act occurred). Arthur sees it drinking from a pool just after he wakes from a disturbing dream that foretells Mordred's destruction of the realm. He is then approached by King Pellinore, who confides that it is his family quest to hunt the Beast. Merlin reveals that the monster had been born of a human woman, a princess who lusted after her own brother. She slept with a devil who had promised to make the boy love her, but the devil manipulated her into accusing her brother of rape. Their father had the brother torn apart by dogs as punishment. Before he died, he prophesied that his sister would give birth to an abomination that would make the same sounds as the pack of dogs that were about to kill him.

In the Post-Vulgate Merlin Continuation and Queste de Saint Grail (Quest for the Holy Grail), the Prose Tristan, and in Thomas Malory's Le Morte d'Arthur, Saracen knight Palamedes hunts the Questing Beast. It is at first a futile venture, much like his love for Tristan's paramour Iseult, offering him nothing but hardship. However, the conversion to Christianity allows Palamedes relief from his endless worldly pursuits, and he finally slays the Beast during the Grail Quest after he, Perceval, and Galahad have chased it into a lake. The Questing Beast story in the Post-Vulgate can be interpreted as a symbol of the incest, violence and chaos that eventually destroys Arthur's kingdom. Scholars also offered some other and different interpretations for Malory's version of the story.