I came up with this because I learned from Tumblr that there’s apparently more than a hundred fanfics for The Epic of Gilgamesh on Ao3, and I think it’s poetic in a way how we’ve still never really gotten over the first story ever.

My answer would be Le Roman de Silence, from the early 1200s, which is about the adventures Silence, a boy who was born as a girl (that’s the author’s way of describing him)and who eventually becomes a knight. I just stumbled across it randomly but I fell in love with it after reading it the first time, and I think it’s beautiful how something 1000 years old can still be around and not have lost any of it’s capability for arousing our emotions.