Amfortas, the custodian of the grail, has been seduced by Kundry and wounded by Klingsor. The wound remains unhealed; no herbs do more than briefly alleviate the pain, as does bathing in the holy lake. Amfortas and the knights of the grail hope for the advent of the promised healer, a pure fool, made wise by pity. The squires abuse the strange, wild woman, Kundry, and Gurnemanz, the oldest of the grail knights - not knowing that it was she who was responsible for Amfortas’ wound - reproves them for their lack of charity; she may be, as they say, accursed, but she now lives under the protection of the grail. She was found almost lifeless in that place by Titurel, father of Amfortas, when he built the grail castle of Monsalvat.

Gurnemanz tells how angels brought the grail and spear to Titurel, to be guarded only by the pure in heart. Klingsor, although aspiring to the grail, was sinful and his self-castration made it impossible for him to serve the grail, though it did give him magic powers, which enabled him to transform the wilderness into a luxuriant garden in which beautiful women ensnared the knights. Parsifal is brought in carrying his bow and arrows, having killed a swan. He does not know who his father was, or even his own name, only that of his mother. Kundry explains that his mother had tried to bring him up cut off from the world, to save him from being killed in battle like his father. He remembers having seen knights and followed them and Kundry tells him that his mother had then died of grief. Hoping that Parsifal may prove to be the pure fool of the prophecy, Gurnemanz takes him to the castle, as the scene changes around them. The covered grail is carried before Amfortas and the voice of Titurel, entombed in the wall, is heard demanding that Amfortas unveil it and allow its powers of renewal to sustain him, but these powers also prolong Amfortas’ life and suffering. He obeys reluctantly and blesses bread and wine which are distributed among the knights. Titurel is refreshed, but Amfortas suffers. Parsifal, who has watched in silent pity, is chased away angrily by Gurnemanz for not having understood anything of what he has seen...