The answer is "Athena".
As per the mythographic abridgment Bibliotheke, diverse stories have mentioned the reason for the blindness of Tiresias, the most direct being that he was essentially blinded by the gods themselves for uncovering their secrets. An elective story told by the writer Pherecydes was followed in Callimachus' ballad "The Bathing of Pallas"; in it, Tiresias was blinded by Athena after he staggered onto her while she was bathing.