In Indiana Jones and the Last Crusade, the unnamed guardian is called the Grail Knight.
The character appears in the temple at the end of the 1989 adventure film and has remained beside the Grail for centuries. He is presented as a medieval knight who took part in the First Crusade and reached the hidden temple containing the sacred cup. His armor, sword, and age emphasize the legendary timespan of his guardianship.
The Grail Knight warns Indiana Jones and the others that the cup must remain concealed. He also explains that the Grail cannot be taken beyond the temple’s great seal. The film does not give him a personal name; “Grail Knight” is the descriptive title used for the character.
He is sometimes confused with a historical crusader or with the fictional knight from earlier Arthurian traditions. In the film, however, he is an original guardian character serving the story’s final test.