Quote Originally Posted by TheCursedQuill

Dumbledore knew, Snape could more than probably guess, and Hagrid in the first book, Remus in the third, and Barty Crouch jr. in the fourth
Snape FOR SURE knows about the cloak, as he uses it in PoA "Severus Snape was pilling off yhe Invisibility Cloak...'I found this at the base of the Whomping Willow,' said Snape, throwing the Cloak aside, careful to keep his wand pointed at Lupin's chest. 'Very useful Potter, I thank you...'" pages 2262-263.