In some versions of the legend that include the search for the Holy Grail, Galahad was the only knight worthy enough to succeed in the quest and find the resting place of the Grail. In fact he found it twice, because in his innocence he didn't realise what he'd found the first time, so he had to go back later and find it again.
The Qufte du Saint Graal, the only romance of which Galahad is the hero, is dependent on and a completion of the Lancelot development of the Arthurian cycle. Lancelot, as lover of Guinevere, could not be permitted to achieve so spiritual an emprise, yet as leading knight of Arthurís court it was impossible to allow him to be surpassed by another. Hence the invention of Galahad, son to Lancelot by the Grail kingís daughter; predestined by his lineage to achieve the quest, foredoomed, the quest achieved, to vanish, a sacrifice to his fatherís fame, which, enhanced by connexion with the Grail winner, could not risk eclipse by his presence. Here the Grail, the chalice of the Last Supper, is at the same time, as in the Gawain stories, self-acting and food-supplying.
Sir Galahad is also the title of a poem by Alfred, Lord Tennyson, which is about the legendary knight. It begins:
My good blade carves the casques of men,
My tough lance thrusteth sure,My strength is as the strength of ten,
Because my heart is pure.
Sir Galahad is also the name of a series of British [Royal Fleet Auxiliary] landing craft, notably including a vessel attacked in the Falklands War with the loss of 48 men. See RFA Sir Galahad (1966) for the original ship and RFA Sir Galahad (1987) for its replacement.