A Medieval character of folklore you might have heard of is Maid Marian, the paramore of Robin Hood. Unlike King Arthur, who was likely not to have been based on a real person, many historians think that there might have been a grain of truth to the character of Robin Hood. The first mentions of this famous outlaw who stole from the rich to give to the poor come from the late 1300s, but legends about him had already been popular by that time.
However, Robin Hood’s lover, Maid Marian, didn’t come into the story until the 16th century. Prior to that, Robin Hood appears to have acted extremely religiously and with a special devotion to the Virgin Mary — who might eventually have been morphed into Maid Marian. It was typical for chivalric literature to feature devotion to Jesus’s mother, as well as to place a noblewoman upon a pedestal and go on about her like a swooning Victorian.
There was also a story of a Maid Marian associated with a Robin from the 13th century, but this tale came from the “pastourelles” (Old French poems often dealing with female sheepherders) and the Robin was a completely different person. Regardless, by 1500 songs and festivities associated with the month of May that featured Maid Marian and Robin Hood were extremely popular in England.
Sources: Woodcut of Maid Marian from 17th c in Wikipedia. You can hear all about the Maid Marian and Robin Hood legends on the podcast “’tis but a Scratch: fact and fiction about the Middle Ages” with host Dr. Richard Abels