Which knight of the Round Table was the son of Lancelot and achieved the Holy Grail? The knight was Galahad.
Galahad is the exceptionally pure and spiritually perfect knight of the Arthurian Grail romances. He is identified as the son of Lancelot and Elaine of Corbenic, the daughter of the Fisher King in many prose traditions. His birth is linked to prophecy: Merlin and other figures foresee that he will surpass his father and complete the quest that Lancelot cannot.
Galahad first appears as a major character in the 13th-century Lancelot-Grail, or Vulgate, Cycle. At Camelot, he takes the vacant Siege Perilous, the dangerous seat reserved for the knight destined to achieve the Holy Grail. He later joins Perceval and Bors in the quest and is the one granted the fullest vision of the sacred vessel.
A common mix-up is choosing Lancelot, who is the greatest worldly knight but is denied the complete Grail because of his adultery with Guinevere. Perceval and Bors also reach the Grail, but Galahad is its principal achiever and ultimately ascends to Heaven after the vision.