Man Friday is one of the main characters of Daniel Defoe's novel Robinson Crusoe. His name, in the novel given to him by Robinson Crusoe (p.244, first edition), has later become an expression used to describe a male personal assistant or servant, especially one who is particularly competent or loyal.
The fictional character is described in the Nuttall Encyclopaedia:
the young savage, attendant on Robinsin Crusoe, so called as discovered on a Friday
Robinson Crusoe spent twenty-four years alone on an island off the coast of Venezuela with his talking parrot Poll, his pet dog, and a tame goat as his only companions. In his twenty-fourth year he discovered that Carib cannibals occasionally arrived on a desolate beach on the island to kill and eat their captives. (The portrayal of Caribs as cannibals is still controversial; as recently as 2006, complaints were made about the portrayal of Caribs in the movie Pirates of the Caribbean 2.)
Crusoe observed one of the Caribs, kept captive and about to be eaten, escaping his captors. When the Carib fled, pursued by two others, Crusoe ambushed them (the cannibals), and the others fled in their canoes. The rescued captive, who was left behind, bowed in gratitude to Crusoe, who decided to employ him as a servant. He named him Friday after the day of the week upon which the rescue took place.
Crusoe describes Friday as being a Native American, though being very unlike the Indians of Brazil and Virginia. His religion involved the worship of a mountain god named Benamuckee, officiated over by high priests called Oowokakee. Friday tolerated cannibalism, and even suggested eating the remains from the ambush.
Crusoe taught Friday the English language and converted him to Christianity. He told him that cannibalism was wrong, and Friday accompanied him in his next ambush on cannibals, in which they saved Friday's father.
Crusoe returned to England twenty-eight years after being shipwrecked on the island, and four years after rescuing Friday. Friday's father went with the Spanish castaway to the mainland to retrieve the other fourteen Spanish castaways, but Crusoe and Friday left the island before they returned.
Friday accompanied Crusoe home to England, and was his companion in the sequel The Further Adventures of Robinson Crusoe, in which Friday is killed in a sea battle against 160 canoes.
In Jules Verne's L'École des Robinsons, the castaways rescue an African Negro on their island who says his name is Carefinotu. Tartelett proposes to call him Mercredi ("Wednesday"), "as it is always done in the islands with Robinsons," but his master Godfrey prefers to keep the original name.
The 1964 film Robinson Crusoe on Mars retold the Robinson Crusoe story as a space adventure. Victor Lundin played the native companion of Crusoe figure Commander Christopher Draper (Paul Mantee), who dubs him 'Friday' in reference to the novel.