Warning: Spoilers ahead for The Green Knight, and its ending and post-credits scene.
A24's The Green Knight ends with a surprise post-credits scene, but who is the girl playing with the king's crown? David Lowery's adaptation of the 14th-century poem "Sir Gawain and the Green Knight" stars Dev Patel as the nephew of King Arthur. The movie follows Gawain's journey to face his likely death at the hand of the powerful Green Knight. The mystical tale shows Gawain's bravery challenged repeatedly as he goes on this quest, with The Green Knight's ending including a vision of what his life could be like if his fear got the best of him and he fled from the potentially fatal swing of Green Knight's ax.
Lowery lets The Green Knight end in a rather ambiguous fashion, though. Gawain decides to confront his fate and take off an enchanted sash that makes him unkillable. But, the movie cuts to black and shows its final title card before the Green Knight brings down his ax on Gawain's neck. This isn't exactly where The Green Knight's story concluded, though, as a post-credits scene briefly is shown at the very end. It starts with the king of Camelot's crown sitting on the floor and ends with an unidentified young girl picking it up. But, audiences will likely be left wondering about the context of this scene and the identity of the girl.
The Green Knight's ending and post-credits scene are purposefully vague as director David Lowery wants audiences to make their own conclusion about what happened to Gawain. The post-credits scene could be Lowery showing his hand as to what his interpretation of the ending is, though. This is the same crown worn by King Arthur for the majority of the film and by Gawain in his vision of the future. While there is a chance this girl is a random Camelot girl or even Arthur's daughter Grega, the more likely outcome is that this is Gawain's daughter in Green Knight's post-credits scene.
Since Sir Gawain is an Arthurian legend figure, the accounts of his life and lineage vary slightly depending on the source of the information. One aspect of Gawain's offspring that is known relates to his children. It is written that Gawain had three sons: Florence, Lovell/Lioniel, and Gingalain/Guinglain. There are also stories about Gawain fathering other children, but the various Arthurian stories do not share any other information beyond their conception. The Green Knight makes plenty of changes to Gawain's story, though, and that includes him having a daughter in his vision of the future. Her appearance in The Green Knight's post-credits scene could be a massive clue that Gawain does survive his second encounter with the Green Knight.
There is a chance that The Green Knight's post-credits scene is actually set in Gawain's vision of the future, making it so his daughter is playing with the crown after he is finally killed and beheaded by his enemies. However, Gawain's acceptance of his participation in the Green Knight's game and what that means could point to the movie's ending lining up more with how the poem ends. Gawain survives the poem and leaves the Green Knight on good terms, even though he is regarded as a coward. Since Gawain accepted his fate at the end of The Green Knight, the mystical figure could spare his life and allow him to carry his newfound perspective on life with him to the throne. That would make The Green Knight's post-credits scene a tease of an alternate life that Gawain leads as king of Camelot, with his daughter (possibly even mothered by Essel) a sign of the happiness he found.