They produced both live action and animated versions of Robin Hood. Note that Robin Hood isn’t a “fairy tale” - it’s a folk hero legend. The story takes place in Britain (and the animated version has an old West folksy narrator 
).
If you’re really hunting for a Disney “Medieval film” - and you’re willing to go with live action - I’d suggest that Dragonslayer qualifies as one of their best. Although it’s sword and sorcery fantasy, it’s pretty clearly set in Britain (not Fairyland), and in the early part of the Medieval era. It also includes really good characters for both young boys and girls to associate with.
For sword and sorcery animated, they also made The Black Cauldron. The books it’s based on take place in Wales, but Disney took serious license with the stories.
EDIT: This response is to both @SmashMartian and @SamWinston - you guys were both discussing the topic, and I want to make sure that Sam gets the answer.
