17th century poet Jean De La Fontaine was clearly inspired by the great fabulists (fable writers) of history. He took their works and expanded on them, cleverly, playfully, and in a nuanced fashion.
We English speakers rely on Elizur Wright's 19th century translations of De La Fontaine's work. (Wright was himself a great man: a mathematician, devoutly religious, and an abolitionist.)
I love these translated pieces as literature more than as lessons. With De La Fontaine's 17th century sensibilities and Wright's 19th century English, they require a little effort. I recommend them especially highly for older kids who will soon be tackling, say, Shakespeare.
De La Fontaine's fables are bite-sized and therefore easier to puzzle out. Besides, you can always refer to the straightforward fables they're based on when you get stuck! (In fact, I'll make a point of referring you to the source fable for each of de la Fontaine's poems.)
Below is a very small sampling of De La Fontaine's work. If you love them like I do, you can always find the complete works: