The Lost Tribe is an (indigenous) ethnic group that lives in (almost) complete isolation from the outside world, oblivious to the existence of modern civilization, technology, and other concepts. However, their way of life may be changed after being contacted by foreign people from the outside world.
- Yu-Gi-Oh! has survivors of Atlantis.
- The B-movie Mexican Blow has Indians from north of the Rio Grande who migrated to southern Mexico to escape the white man and speak English so they won't be tricked by the white man again. All the Indians are white, but the main character is a Mighty Whitey too.
- At Play In The Fields of the Lord has theories that the Niaruna are the Lost Tribes of Israel or a lost tribe of Sioux.
- Star Wars Legends: Kind of a Justified Trope when you've got Casual Interstellar Travel; there's a hell of a lot of galaxy to lose yourselves in, intentionally or otherwise.
- The titular lost tribe in the Stargate Atlantis episode "The Lost Tribe".
- The Goodies: In "The Lost Tribe of the Orinoco", the Goodies go in search of the eponymous lost tribe and find it in a most unexpected location.
- The lost tribes of Israel are the Trope Namer. Either in The Bible or The Book of Mormon. Mormons believe that American Indians are descended from Jews.
- More accurately, descended from Manassites who lived in Jerusalem. Europeans are mostly descended from Ephraim, so most people in the Americas are from Joseph.
- In New Age beliefs, American Indians are aliens.
- Chrono Trigger has a lost tribe of Mystics, and survivors of the Kingdom Of Zeal.
- Final Fantasy likes to use this trope:
- In the Marathon franchise, ten clans of S'pht were living on planet Lh'owon when the it was conquered by the Pfhor, who then enslaved the S'pht. The was a legendary eleventh clan, the S'pht'Kr, who left Lh'owon prior to the Pfhor invasion. Late in hte seond game the S'pht'Kr are found and return to Lh'owon to liberate their brethren.
- The Legend of Dragoon has the last surviving dragons.
- Uzo and Muzo are the last survivors of the Mt. Gokuho clan in the game Kingdom of Paradise. Shinbu makes them lost for good.
- Wikipedia has an article on this subject.
- Perhaps the best example of this trope in real life are the Sentinelese tribe, which may very well be the most isolated group of indigenous people on Earth. They live on North Sentinel Island in the Andaman Islands of India, living a hunter-gatherer lifestyle that hasn't changed much since the Stone Age. They violently reject all attempts at contact, shooting at any outsiders with arrows. Because of that, we know next to nothing about them, including their culture, language, and religion. The last official attempt at contact was made in the mid 1990s, and since then they've been left alone, and it's very unlikely that will change anytime soon. Their numbers may or may not have been culled considerably by the 2004 Indian Ocean tsunami, but good luck trying to find out yourself. The last person to set foot on the island, an American Christian missionary named John Allen Chau in late 2018, was killed by the natives when he trespassed and refused to leave.
- Lost tribes of Native North Americans are found all the time. They live like modern people and are really not all that different.
- Previously unknown offshoots of the Jewish diaspora show up every decade or so.